sound: fix oss/msnd_pinnacle module param type

Fix module parameter data type to eliminate build warning.

sound/oss/msnd_pinnacle.c:1727:1: warning: return from incompatible pointer type

Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Takashi Iwai <tiwai@suse.de>