ALSA: sound/isa/gus: Correct code taking the size of a pointer

sizeof(share_id) is just the size of the pointer.  On the other hand,
block->share_id is an array, so its size seems more appropriate.

A simplified version of the semantic patch that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
expression *x;
expression f;
type T;
@@

*f(...,(T)x,...)
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/isa/gus/gus_mem.c

@@ -127,7 +127,8 @@ static struct snd_gf1_mem_block *snd_gf1_mem_share(struct snd_gf1_mem * alloc,
 	    !share_id[2] && !share_id[3])
 		return NULL;
 	for (block = alloc->first; block; block = block->next)
-		if (!memcmp(share_id, block->share_id, sizeof(share_id)))
+		if (!memcmp(share_id, block->share_id,
+				sizeof(block->share_id)))
 			return block;
 	return NULL;
 }