docs: add expbf16 higher math function

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

Author: krishna2803

libc/docs/headers/math/index.rst

@@ -289,7 +289,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | cosh      | |check|          |                 |                        | |check|              |                        |                        | 7.12.5.4               | F.10.2.4                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
-| cospi     | |check|          |                 |                        | |check|              |                        |                        | 7.12.4.12              | F.10.1.12                  |
+| cospi     | |check|          |                 |                        | |check|              |                        | |check|                | 7.12.4.12              | F.10.1.12                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+
 | dsqrt     | N/A              | N/A             |   |check|              | N/A                  |       |check|\*        |                        | 7.12.14.6              | F.10.11                    |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+------------------------+----------------------------+