V4L/DVB (10405): saa7134-core: loading saa7134-alsa is now the default

Most boards nowadays supports saa7134-alsa. Even some of they doesn't have any
option to wire an audio cable. So, lets load saa7134-alsa by default, if the
board is not based on saa7130 and if saa7134-alsa is compiled.

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