ALSA: hda - Fix runtime PM check

The device can support runtime PM no matter whether it support
signal wakeup or not. For some chips like Haswell which doesnot
support PME by default, this patch let haswell Display HD-A controller
enter runtime suspend, and bring more power saving whith power-well
feature enabled.

Signed-off-by: Wang Xingchao <xingchao.wang@linux.intel.com>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>