media: v4l uapi docs: few minor corrections and typos

Do a series of minor corrections at the V4L2 uAPI documentation.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>