docs: add next{after,down,toward,up}bf16 math functions

Signed-off-by: Krishna Pandey <[email protected]>

Author: krishna2803

libc/docs/headers/math/index.rst

@@ -215,13 +215,13 @@ Basic Operations
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | nearbyint        | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.9.3               | F.10.6.3                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nextafter        | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.11.3              | F.10.8.3                   |
+| nextafter        | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.11.3              | F.10.8.3                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nextdown         | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.11.6              | F.10.8.6                   |
+| nextdown         | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.11.6              | F.10.8.6                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nexttoward       | |check|          | |check|         | |check|                | |check|              | N/A                    |                        | 7.12.11.4              | F.10.8.4                   |
+| nexttoward       | |check|          | |check|         | |check|                | |check|              | N/A                    | |check|                | 7.12.11.4              | F.10.8.4                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| nextup           | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.11.5              | F.10.8.5                   |
+| nextup           | |check|          | |check|         | |check|                | |check|              | |check|                | |check|                | 7.12.11.5              | F.10.8.5                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | remainder        | |check|          | |check|         | |check|                | |check|              | |check|                |                        | 7.12.10.2              | F.10.7.2                   |
 +------------------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+