Documentation: userspace-api: correct spelling

Correct spelling problems for Documentation/userspace-api/ as reported
by codespell.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: Sean Young <sean@mess.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Cc: linux-media@vger.kernel.org
Link: https://lore.kernel.org/r/20230129231053.20863-10-rdunlap@infradead.org


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