The current fixup for dell-bios model with STAC9228 codec contains the
override of pin 0x0c for analog mic.  But this is actually just adding
a bogus pin and confuses the parser.  Better to remove it for the
auto-mic switching.

Meanwhile, for a possible regression, keep the old configuration as
model=dell-bios-amic, so that people can test it again quickly.

Tested on Dell 1420n laptop.
Reported-and-tested-by: Eric Shattow <lucent@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>