ALSA: hda: fix mute led polarity for HP laptops with buggy BIOS

Some HP laptop models do not have a properly filled OEM string used
to set the gpio and polarity of the mute led. Make the mute led
configuration work for this case.

Signed-off-by: Gustavo Maciel Dias Vieira <gustavo@sagui.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>