This patch improves the generic parser code to allow to set up the
headphone jack as a mic input.  User can enable this feature by giving
hp_mic hint string.

The former shared hp/mic feature for the single built-in mic is still
retained.  This detection can be disabled now via hp_mic_detect hint
string, too.
Signed-off-by: Takashi Iwai <tiwai@suse.de>