Introduce the concept of a "gated" jack.  The gated jack's pin sense
is
only valid when the "gating" jack is plugged.  This requires checking
the gating jack when the gated jack changes and re-checking the gated
jack when the gating jack is plugged/unplugged.

This allows handling of devices where the mic jack detect floats when
the headphone jack is unplugged.

[Rewritten for fixing the possible snd_array reallocation, covering
 the missing callback calls and jack sync operations, as well as some
 code cleanups -- tiwai]
Signed-off-by: Dylan Reid <dgreid@chromium.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>