[media] Improve media Kconfig menu

I've always found it very confusing that the "Media ancillary drivers (tuners,
sensors, i2c, frontends)" comment came after the "Autoselect" option. This patch
moves it up and changes the "Autoselect" text to correspond more closely to
the "Media ancillary drivers" comment.
It also fixes two typos.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>