ALSA: maestro3: Proper endian notations

The ASSP data passed to maestro3 driver is in little-endian format,
hence the data pointer should be with __le16.

Spotted by sparse, warnings like:
  sound/pci/maestro3.c:2128:35: warning: cast to restricted __le16

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