drm/edid: Use kmemdup instead of kmalloc + memcpy

This issue was reported by coccicheck using the semantic patch
at scripts/coccinelle/api/memdup.cocci
Signed-off-by: NBenoit Taine <benoit.taine@lip6.fr>
Signed-off-by: NDave Airlie <airlied@redhat.com>

drivers/gpu/drm/drm_edid.c

@@ -3228,10 +3228,9 @@ int drm_edid_to_speaker_allocation(struct edid *edid, u8 **sadb)
 
 			/* Speaker Allocation Data Block */
 			if (dbl == 3) {
-				*sadb = kmalloc(dbl, GFP_KERNEL);
+				*sadb = kmemdup(&db[1], dbl, GFP_KERNEL);
 				if (!*sadb)
 					return -ENOMEM;
-				memcpy(*sadb, &db[1], dbl);
 				count = dbl;
 				break;
 			}