[media] rtl28xxu: add Gigabyte U7300 DVB-T Dongle

Device with ID 1b80:d393 is the Gigabyte U7300 DVB-T dongle.
It contains decoder Realtek RTL2832U and tuner Fitipower FC0012.

[crope@iki.fi: fix trivial merge conflict]
Signed-off-by: Alexander Inyukhin <shurick@sectorb.msk.ru>
Signed-off-by: Antti Palosaari <crope@iki.fi>

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>