ALSA: hda: Rename back to dmic_detect option

ALSA: hda: Rename back to dmic_detect option

We've got quite a few bug reports showing the SOF driver being loaded
unintentionally recently, and the reason seems to be that users didn't
know the module option change: with the recent kernel, a new option
dsp_driver=1 has to be passed to a new module snd-intel-dspcfg
instead of snd_hda_intel.dmic_detect=0 option.

That is, actually there are two tricky things here:
- We changed the whole detection in another module and another
  option semantics.
- The existing option for skipping the DSP probe was also renamed.

For avoiding the confusion and giving user more hint, this patch
reverts the renamed option dsp_driver back to dmic_detect for
snd-hda-intel module, and show the warning about the module option
change when the non-default value is passed.

Fixes: 82d9d54a6c0e ("ALSA: hda: add Intel DSP configuration / probe code")
Link: https://lore.kernel.org/r/20200109082000.26729-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>