V4L/DVB (10179): tda8290: Fix two sparse warnings

/home/v4l/master/v4l/tda8290.c:233:7: warning: symbol 'i' shadows an earlier one
/home/v4l/master/v4l/tda8290.c:178:3: warning: symbol 'fm_mode' was not declared. Should it be static?

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