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

Documentation/kernel-hacking/locking.rst

@@ -295,7 +295,7 @@ Pete Zaitcev gives the following summary:
 
 -  If you are in a process context (any syscall) and want to lock other
    process out, use a mutex. You can take a mutex and sleep
-   (``copy_from_user*(`` or ``kmalloc(x,GFP_KERNEL)``).
+   (``copy_from_user()`` or ``kmalloc(x,GFP_KERNEL)``).
 
 -  Otherwise (== data can be touched in an interrupt), use
    spin_lock_irqsave() and