ALSA: hda: Use position_fix=1 for Acer Aspire 5538 to enable capture on internal mic

BugLink: https://launchpad.net/bugs/685161



The reporter of the bug states that he must use position_fix=1 to enable
capture for the internal microphone, so set it for his machine's PCI
SSID.  Verified using 2.6.35 and the 2010-12-04 alsa-driver build.

Reported-and-tested-by: Ralph Wabel <rwabel@gmx.net>
Cc: <stable@kernel.org>
Signed-off-by: Daniel T Chen <crimsun@ubuntu.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>