docs: fix typo in Documentation/kernel-hacking/locking.rst

Change copy_from_user*( to copy_from_user() .

Signed-off-by: Takahiro Itazuri <itazur@amazon.com>
Link: https://lore.kernel.org/r/20220124081447.34066-1-itazur@amazon.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>