[media] mtk_vcodec_dec: return error at mtk_vdec_pic_info_update()

Gcc 7.1 complains that:

	drivers/media/platform/mtk-vcodec/mtk_vcodec_dec.c: In function 'mtk_vdec_pic_info_update':
	drivers/media/platform/mtk-vcodec/mtk_vcodec_dec.c:284:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
	  int ret;
	      ^~~

Indeed, if debug is disabled, "ret" is never used. The best
fix for it seems to make the fuction to return an error code.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/mtk-vcodec/mtk_vcodec_dec.c

@@ -278,7 +278,7 @@ static void mtk_vdec_flush_decoder(struct mtk_vcodec_ctx *ctx)
 	clean_free_buffer(ctx);
 }
 
-static void mtk_vdec_pic_info_update(struct mtk_vcodec_ctx *ctx)
+static int mtk_vdec_pic_info_update(struct mtk_vcodec_ctx *ctx)
 {
 	unsigned int dpbsize = 0;
 	int ret;
@@ -288,7 +288,7 @@ static void mtk_vdec_pic_info_update(struct mtk_vcodec_ctx *ctx)
 				&ctx->last_decoded_picinfo)) {
 		mtk_v4l2_err("[%d]Error!! Cannot get param : GET_PARAM_PICTURE_INFO ERR",
 				ctx->id);
-		return;
+		return -EINVAL;
 	}
 
 	if (ctx->last_decoded_picinfo.pic_w == 0 ||
@@ -296,12 +296,12 @@ static void mtk_vdec_pic_info_update(struct mtk_vcodec_ctx *ctx)
 		ctx->last_decoded_picinfo.buf_w == 0 ||
 		ctx->last_decoded_picinfo.buf_h == 0) {
 		mtk_v4l2_err("Cannot get correct pic info");
-		return;
+		return -EINVAL;
 	}
 
 	if ((ctx->last_decoded_picinfo.pic_w == ctx->picinfo.pic_w) ||
 	    (ctx->last_decoded_picinfo.pic_h == ctx->picinfo.pic_h))
-		return;
+		return 0;
 
 	mtk_v4l2_debug(1,
 			"[%d]-> new(%d,%d), old(%d,%d), real(%d,%d)",
@@ -316,6 +316,8 @@ static void mtk_vdec_pic_info_update(struct mtk_vcodec_ctx *ctx)
 		mtk_v4l2_err("Incorrect dpb size, ret=%d", ret);
 
 	ctx->dpb_size = dpbsize;
+
+	return ret;
 }
 
 static void mtk_vdec_worker(struct work_struct *work)