ALSA: hda - Always allow access for POWER_STATE verbs via regmap

The hdac regmap code checks whether the codec is powered on while
accessing, but there must be an exception -- the verbs to control the
power state.

Currently HD-audio driver doesn't access them via regmap, so this
patch doesn't fix any current behavior, but it's just for future.

Signed-off-by: Takashi Iwai <tiwai@suse.de>