ALSA: hda/intel: Drop superfluous AZX_DCAPS_I915_POWERWELL checks

snd_hdac_display_power() can be called even for a HDA controller
without DRM binding.  The same is true for other helpers,
snd_hdac_i915_set_bclk() and snd_hdac_set_codec_wakeup().
So all superfluous AZX_DCAPS_I915_POWERWELL  checks in hda_intel.c can
be dropped, and the definition of AZX_DCAPS_I915_POWERWELL itself can
be removed as well.  This simplifies the code a lot.

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