ALSA: intel8x0: move virtual environment detection code into one place

This is refactoring patch: preparation for add improved detection code.
Now all detection code placed in one place.

Signed-off-by: Konstantin Ozerkov <kozerkov@parallels.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>