[ALSA] fix cs5535 section mismatch

snd_cs5535audio_mixer() is only called by __devinit snd_cs5535audio_probe(),
so the mixer function can also be __devinit.
WARNING: vmlinux.o(.text+0xfdbba0): Section mismatch: reference to .init.data:ac97_quirks (between 'snd_cs5535audio_mixer' and 'process_bm0_irq')

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>