ALSA: hda_intel: add AZX_DCAPS_I915_POWERWELL for SKL and BSW

HDMI/DP codec on SKL/BSW is in the power well.
The power well must be turned on before probing the
HDMI/DP codec.

This is a temporary patch, which will power on the
powerwell by adding AZX_DCAPS_I915_POWERWELL for SKL
and BSW. After restructuring and new flag is added,
this patch will be reverted.

Signed-off-by: Libin Yang <libin.yang@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>