ALSA: atiixp_modem: Proper endian notations

The DMA address table in atiixp modem driver is in little-endian,
hence we should define it with __le32 properly.

Spotted by sparse, a warning like:
  sound/pci/atiixp_modem.c:360:28: warning: incorrect type in assignment (different base types)

Signed-off-by: Takashi Iwai <tiwai@suse.de>