ALSA: audio_codec: add hwdep interface

This commit adds hwdep interface for codec calibration.

currently codec driver uses request_firmware to get calibration data
but as this firmware file is also written by userspace process after
bootup, it is not recommended to use request_firmware. ALSA core
provides mechanism to get hardware dependent data using hwdep nodes.
Codec will use aforementioned nodes to get calibration data from
userspace.

Change-Id: I6d835a5071c3c71dd77e9ed08cf6b11143517053
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>