V4L/DVB (11925): em28xx: Add support for the K-World 2800d

Make the KWorld 2800d work properly.  In this case, that means making the
profile more generic so that it works for both the Pointnix Intra-Oral USB
camera and the KWorld device.

The device provides the audio through a pass-thru cable, so we don't need
an actual audio capture profile (neither the K-World device nor the Pointnix
have an onboard audio decoder).

Thanks to Paul Thomas for providing sample hardware.

Cc: Paul Thomas <pthomas8589@gmail.com>
Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>