This essentially reverts the commits
  c337104b ("ALSA: HD-Audio: SKL+: abort probe if DSP is present
  and Skylake driver selected")
and
  d82b51c8 ("ALSA: HD-Audio: SKL+: force HDaudio legacy or SKL+
  driver selection")
for the path of legacy HD-audio controller (snd-hda-intel).

The automatic DSP detection and skip of binding with the legacy driver
caused regressions on several machines like Dell XPS13.  They give the
PCI class 0x40380 indicating the availability of DSP while they don't
work with ASoC SKL driver (yet).

As the support of ASoC driver for such devices isn't available, it's
better to revert the whole DSP-detection-and-skip behavior of the
legacy driver, so that we can get the old good driver working on such
devices.

The pci_binding option for ASoC SKL driver is still kept so that it
can work without blacklisting.

Fixes: c337104b ("ALSA: HD-Audio: SKL+: abort probe if DSP is present and Skylake driver selected")
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: Hans de Goede <hdegoede@redhat.com>
Reported-by: Azat Khuzhin <dohardgopro@gmail.com>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>