ALSA: hda: Copying sync power state helper to core

The current sync_power_state is local to hda code, moving it
core so that other users apart from hda legacy can use it.
The helper function ensures the actual state reaches the target state.

Signed-off-by: Abhijeet Kumar <abhijeet.kumar@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>