[media] m88rs2000: Correct m88rs2000_set_fec settings

Register 0x70 is used to set fec, register 0x76 is used to get fec

Register 0x76 is set to 0x8.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>