[media] au8522: cleanup s-video settings at setup_decoder_defaults()

setup_decoder_defaults() doesn't really care about the input
port. All it needs to know is if the input port is s-video or
not.

As the caller function already knows that, just pass a boolean
instead.

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