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

drivers/media/pci/ivtv/ivtv-alsa-main.c:208:5: warning: no previous prototype for 'ivtv_alsa_load' [-Wmissing-prototypes]
drivers/media/pci/ivtv/ivtv-alsa-pcm.c:325:5: warning: no previous prototype for 'snd_ivtv_pcm_create' [-Wmissing-prototypes]
drivers/media/pci/ivtv/ivtv-alsa-pcm.c:72:6: warning: no previous prototype for 'ivtv_alsa_announce_pcm_data' [-Wmissing-prototypes]
drivers/media/pci/ivtv/ivtv-firmware.c:279:5: warning: no previous prototype for 'ivtv_firmware_restart' [-Wmissing-prototypes]
drivers/media/pci/ivtv/ivtv-ioctl.c:1171:5: warning: no previous prototype for 'ivtv_s_std' [-Wmissing-prototypes]

Cc: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>