ALSA: intel8x0: Skip ac97 clock measurement on VM

The intel8x0 driver tries to measure the AC97 bus clock at the probe
time because there have been machines that are driven in different
rate (44.1kHz vs 48kHz).  This was the past and currently most of
usages of this driver are on VM, and those are certainly fixed with
48k clock, hence it's useless and waste of time to measure.

This patch is an optimization, setting the fixed 48k rate if it's
detected to be running on a VM.

Link: https://lore.kernel.org/r/20210712093641.29079-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>