ALSA: oxygen: add PEX8111 initialization

Configure the PEX8111 bridge on the PCI Express cards so that the audio
DMA controller can do proper burst reads and is less likely to lose
data.  This is usually done automatically, but is required on older
cards where the user has not applied the PLX firmware update.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>