Some VIA codecs like VT1708S have Mic boost amps in the mic pins but
they aren't exposed in the capability bits.  In the past driver code,
we override the pin caps and create mic boost controls forcibly.
While transition to the generic parser, we lost the mic boost controls
although the pin caps are still overridden, because the generic parser
code checks the widget caps, too.

So this patch adds a new helper function to allow the override of the
given widget capability bits, and makes VIA codecs driver to add the
missing input-amp capability bit.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=59861
Cc: <stable@vger.kernel.org> [v3.9+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>