[media] mn88472: move out of staging to media

Move mn88472 DVB-T/T2/C demod driver out of staging to media.

v2: Fix build error reported by kbuild test robot:
drivers/staging/media/mn88472/Makefile: No such file or directory

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>