[media] Add carrier offset calculation for DVB-T

Adding cxd2841er_get_carrier_offset_t to calculate DVB-T offset
for Sony demodulators CXD2841ER and CXD2854ER

Signed-off-by: Abylay Ospan <aospan@netup.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>