Documentation: Fix spelling mistake in hacking.rst

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

Signed-off-by: Mushahid Hussain <mushi.shar@gmail.com>
Link: https://lore.kernel.org/r/20221017112026.88324-1-mushi.shar@gmail.com


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