[ALSA] emu10k1 - Enable side surround channels for Audigy2 EX

Modules: EMU10K1/EMU10K2 driver

Enable side surround channels for Audigy2 EX.  Tested by Rick Wright
<riwright@vt.edu>.

Signed-off-by: Lee Revell <rlrevell@joe-job.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>