ALSA: ASoC - Fix symbol conflicts in omac-mcbsp.c

Add snd_ prefix to avoid the conflict of symbols in omac-mcbsp.c:
  sound/soc/omap/omap-mcbsp.c:503: error: static declaration of 'omap_mcbsp_init' follows non-static declaration
  arch/arm/plat-omap/include/mach/mcbsp.h:373: error: previous declaration of 'omap_mcbsp_init' was here

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