Documentation/locking/locktypes: fix the typo

We have three categories locks, not two.

Signed-off-by: Huang Shijie <[email protected]>
Acked-by: Will Deacon <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jonathan Corbet <[email protected]>

Author: Huang Shijie

Documentation/locking/locktypes.rst

@@ -10,7 +10,7 @@ Introduction
 ============
 
 The kernel provides a variety of locking primitives which can be divided
-into two categories:
+into three categories:
 
  - Sleeping locks
  - CPU local locks