Currently the GPIO bits are managed by individual verbs in some cases
while toggled dynamically in other cases.  For simplifying the GPIO
management, define the GPIO mask, dir and data bits in alc_spec
fields, and refer to / set them consistently from all places.

As a first step, along with the definition of the new gpio_* fields,
this patch replaces the static verbs that are used at initialization
and fixups with the common helper functions.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>