ALSA: hdmi - fix surround41 channel mapping

Channel 2 and channel 3 were all wrongly mapped to HDMI slot 4.
This shows up as a bug that one channel is "lost" when playing in
surround41 mode.

Signed-off-by: Jerry Zhou <jerry.zhou@intel.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>