[media] tda10071: get rid of warning: no previous prototype

drivers/media/dvb-frontends/tda10071.c:119:5: warning: no previous prototype for 'tda10071_rd_reg_mask' [-Wmissing-prototypes]
drivers/media/dvb-frontends/tda10071.c:99:5: warning: no previous prototype for 'tda10071_wr_reg_mask' [-Wmissing-prototypes]

Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>