ALSA: hda: split snd_hda_codec_new function

Split snd_hda_codec_new into two separate functions.
snd_hda_codec_device_init allocates memory and registers with bus.
snd_hda_codec_device_new initialializes the fields and performs
snd_device_new. This enables reuse of legacy HDA codec drivers as ASoC
codec drivers.

In addition mark some functions with EXPORT_SYMBOL_GPL so that it can
be called by ASoC wrapper around the legacy HDA driver (hdac_hda).

Signed-off-by: Rakesh Ughreja <rakesh.a.ughreja@intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>