V4L/DVB (9268): tuner: add FMD1216MEX tuner

This tuner was already supported by proxy as an FMD1216ME, however,
the MEX uses a different FM Radio IF so this addition is now required.

Signed-off-by: Darron Broad <darron@kewl.org>
Signed-off-by: Steven Toth <stoth@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>