snd-hda-intel driver tries to bind with i915 audio component always
when AZX_DCAPS_I915_POWERWELL is set in the driver caps.  This was
mostly OK in the past, as the flag was applied only to a limited set
of devices, namely, Haswell and Broadwell.  On these machines, i915
graphics is almost mandatory as long as HDMI/DP is concerned.

Recently the application of i915 binding was widened to more Intel
chips.  On these chips, the chance of a kernel without i915 graphics
is much higher, and such user would hit an error like:

 snd_hda_intel 0000:00:1b.0: failed to add i915 component master (-19)

Although the error itself is harmless, it's certainly superfluous even
to try binding with i915, if we already know that there isn't any.

This patch fixes it by simply defining AZX_DCAPS_I915_POWERWELL as 0
in the case without i915.  Then all codes referring to this flag will
be optimized out by the compiler.

Fixes: 6603249d ('ALSA: hda - Enable audio component for old Intel PCH devices')
Reported-by: kernel test robot <ying.huang@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>