media/radio: New driver for the radio FM module on Miro PCM20 sound card

media/radio: New driver for the radio FM module on Miro PCM20 sound card

This is recreated driver for the FM module found on Miro
PCM20 sound cards. This driver was removed around the 2.6.2x
kernels because it relied on the removed OSS module. Now, it
uses a current ALSA module (snd-miro) and is adapted to v4l2
layer.

It provides only basic functionality: frequency changing and
FM module muting.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Reviewed-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>