media: cetrus: return an error if alloc fails

As warned by smatch:

	drivers/staging/media/sunxi/cedrus/cedrus.c: drivers/staging/media/sunxi/cedrus/cedrus.c:93 cedrus_init_ctrls() error: potential null dereference 'ctx->ctrls'.  (kzalloc returns null)

While here, remove the memset(), as kzalloc() already zeroes the
struct.
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Acked-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/staging/media/sunxi/cedrus/cedrus.c

@@ -72,7 +72,8 @@ static int cedrus_init_ctrls(struct cedrus_dev *dev, struct cedrus_ctx *ctx)
 	ctrl_size = sizeof(ctrl) * CEDRUS_CONTROLS_COUNT + 1;
 
 	ctx->ctrls = kzalloc(ctrl_size, GFP_KERNEL);
-	memset(ctx->ctrls, 0, ctrl_size);
+	if (!ctx->ctrls)
+		return -ENOMEM;
 
 	for (i = 0; i < CEDRUS_CONTROLS_COUNT; i++) {
 		struct v4l2_ctrl_config cfg = { 0 };