[media] mtk-vcodec: fix some smatch warnings

Fix this bug:
	drivers/media/platform/mtk-vcodec/vdec_drv_if.c:38 vdec_if_init() info: ignoring unreachable code.

With is indeed a real problem that prevents the driver to work!

While here, also remove an used var, as reported by smatch:

	drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_pm.c: In function 'mtk_vcodec_init_dec_pm':
	drivers/media/platform/mtk-vcodec/mtk_vcodec_dec_pm.c:29:17: warning: variable 'dev' set but not used [-Wunused-but-set-variable]
	  struct device *dev;
	                 ^~~
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

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

@@ -26,14 +26,12 @@ int mtk_vcodec_init_dec_pm(struct mtk_vcodec_dev *mtkdev)
 {
 	struct device_node *node;
 	struct platform_device *pdev;
-	struct device *dev;
 	struct mtk_vcodec_pm *pm;
 	int ret = 0;
 
 	pdev = mtkdev->plat_dev;
 	pm = &mtkdev->pm;
 	pm->mtkdev = mtkdev;
-	dev = &pdev->dev;
 	node = of_parse_phandle(pdev->dev.of_node, "mediatek,larb", 0);
 	if (!node) {
 		mtk_v4l2_err("of_parse_phandle mediatek,larb fail!");

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

@@ -31,6 +31,7 @@ int vdec_if_init(struct mtk_vcodec_ctx *ctx, unsigned int fourcc)
 	switch (fourcc) {
 	case V4L2_PIX_FMT_H264:
 	case V4L2_PIX_FMT_VP8:
+		break;
 	default:
 		return -EINVAL;
 	}