V4L/DVB (10177): Fix sparse warnings on em28xx

/home/v4l/master/v4l/em28xx-core.c:396:25: warning: symbol 'outputs' was not declared. Should it be static?
/home/v4l/master/v4l/em28xx-input.c:324:6: warning: symbol 'em28xx_ir_start' was not declared. Should it be static?
/home/v4l/master/v4l/em28xx-cards.c:1925:5: warning: symbol 'em28xx_init_dev' was not declared. Should it be static?

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