ALSA: hda - chmap helper args modified to use generic hdac objs.

Chmap helper arguments are modified to use either hdac_device
object or hdac_chmap object instead of codec specific object.
With this moving these APIs to core will be easier.

Helper added to access a specific channel_allocation object
instead of directly accessing.

Signed-off-by: Subhransu S. Prusty <subhransu.s.prusty@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>