Fix two typos in kernel-docs.rst

Signed-off-by: Andrew Klychkov <andrew.a.klychkov@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://lore.kernel.org/r/20201202074938.GA35075@spblnx124.lan


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