[ALSA] sound/synth/util_mem.c: remove pointless check

The Coverity checker spotted that if anyone would call this function
with 'prev == NULL', he would still get an Oops a few lines below.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/synth/util_mem.c b/sound/synth/util_mem.c
index 1d9b11f..6fc3d2b 100644
--- a/sound/synth/util_mem.c
+++ b/sound/synth/util_mem.c
@@ -116,7 +116,7 @@
 	if (blk == NULL)
 		return NULL;
 
-	if (! prev || prev == &hdr->block)
+	if (prev == &hdr->block)
 		blk->offset = 0;
 	else {
 		struct snd_util_memblk *p = get_memblk(prev);