[media] au0828: get rid of warning: no previous prototype

drivers/media/usb/au0828/au0828-cards.c:28:6: warning: no previous prototype for 'hvr950q_cs5340_audio' [-Wmissing-prototypes]
drivers/media/usb/au0828/au0828-video.c:161:6: warning: no previous prototype for 'au0828_uninit_isoc' [-Wmissing-prototypes]
drivers/media/usb/au0828/au0828-video.c:200:5: warning: no previous prototype for 'au0828_init_isoc' [-Wmissing-prototypes]
drivers/media/usb/au0828/au0828-video.c:786:5: warning: no previous prototype for 'au0828_analog_stream_enable' [-Wmissing-prototypes]
drivers/media/usb/au0828/au0828-video.c:813:6: warning: no previous prototype for 'au0828_analog_stream_reset' [-Wmissing-prototypes]
drivers/media/usb/au0828/au0828-video.c:916:6: warning: no previous prototype for 'au0828_vid_buffer_timeout' [-Wmissing-prototypes]
drivers/media/usb/au0828/au0828-video.c:940:6: warning: no previous prototype for 'au0828_vbi_buffer_timeout' [-Wmissing-prototypes]

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