[media] tda18271c2dd.c: get rid of warning: no previous prototype

drivers/media/dvb-frontends/tda18271c2dd.c:1224:22: warning: no previous prototype for 'tda18271c2dd_attach' [-Wmissing-prototypes]

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