ALSA: hda - Fix build error without CONFIG_SND_HDA_HWDEP=y

CONFIG_SND_HDA_POWER_SAVE is independent from CONFIG_SND_HDA_HWDEP.
Thus snd_hda_hwdep_add_power_sysfs() needs the check of both kconfigs.

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