[media] au0828: add au0828_rc_*() stubs for VIDEO_AU0828_RC disabled case

Define au0828_rc_*() stubs to avoid compile errors when
VIDEO_AU0828_RC is disabled and avoid the need to enclose
au0828_rc_*() in ifdef CONFIG_VIDEO_AU0828_RC in .c files.

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>