[ALSA] sound: hdspm.c fix returning void expression warnings

Just drop the returns.
sound/pci/rme9652/hdspm.c:1031:3: warning: returning void-valued expression
sound/pci/rme9652/hdspm.c:1033:3: warning: returning void-valued expression

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>