[media] tda10086: change typecast to u64 to avoid smatch warnings

drivers/media/dvb-frontends/tda10086.c:476 tda10086_get_frontend() warn: should 'tda10086_read_byte(state, 81) << 8' be a 64 bit type?

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