[ALSA] sound/core/control.c: remove dead code

This patch removes some obviously dead code spotted by the Coverity
checker.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>