ALSA: oxygen: rewrite PCIe bridge initialization

Change the PCIe/PCI bridge initialization code to configure only the
bridge that is actually connected to the sound chip, instead of any
bridge found in the system.  The new code also makes it easier to add
other bridges.

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