V4L/DVB (6687): saa7134: add mute support for radio/analog-in on MD9717 and MD7134

V4L/DVB (6687): saa7134: add mute support for radio/analog-in on MD9717 and MD7134

Currently the saa7134 chips only have mute support for the TV input.

Cards with mute from external audio muxes are already fine on the
other inputs and some recent tuners mute at least the radio on exit.
But these mostly hybrid tuners are not fully backward compatible, since
they must power down and mute regardless.

For some included above, the MD7134 knows several, to switch on mute/automute
to the TV input is functional and backward compatible for the applications,
except that the tuners with tda9887 always mute on exit.

Signed-off-by: Hermann Pitton <hermann-pitton@arcor.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>