Documentation: Fix spelling mistake in hacking.rst

Fix `botton half locks` to `bottom half locks`.

Signed-off-by: Mushahid Hussain <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jonathan Corbet <[e-mail]>

Documentation/kernel-hacking/hacking.rst

···
 .. warning::
 
     Beware that this will return a false positive if a
-    :ref:`botton half lock <local_bh_disable>` is held.
+    :ref:`bottom half lock <local_bh_disable>` is held.
 
 Some Basic Rules
 ================