media: exynos4-is: properly initialize frame format

We copy the subdev frame format from a partially initialized
structure, which is not entirely well-defined. Older compilers
like gcc-4.4 can copy uninitialized stack data here and warn
about it:

drivers/media/platform/exynos4-is/fimc-isp.c: In function 'fimc_isp_subdev_open':
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.reserved[10u]' may be used uninitialized in this function
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.reserved[9u]' may be used uninitialized in this function
...
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.reserved[0u]' may be used uninitialized in this function
drivers/media/platform/exynos4-is/fimc-isp.c:379: error: 'fmt.xfer_func' may be used uninitialized in this function

On newer compilers, only the initialized fields get copied, but
we should not rely on that, so this changes the code to zero-out
the remaining fields first.

Fixes: 9a761e43 ("[media] exynos4-is: Add Exynos4x12 FIMC-IS driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/exynos4-is/fimc-isp.c

@@ -366,16 +366,16 @@ static int fimc_isp_subdev_s_power(struct v4l2_subdev *sd, int on)
 static int fimc_isp_subdev_open(struct v4l2_subdev *sd,
 				struct v4l2_subdev_fh *fh)
 {
-	struct v4l2_mbus_framefmt fmt;
 	struct v4l2_mbus_framefmt *format;
+	struct v4l2_mbus_framefmt fmt = {
+		.colorspace = V4L2_COLORSPACE_SRGB,
+		.code = fimc_isp_formats[0].mbus_code,
+		.width = DEFAULT_PREVIEW_STILL_WIDTH + FIMC_ISP_CAC_MARGIN_WIDTH,
+		.height = DEFAULT_PREVIEW_STILL_HEIGHT + FIMC_ISP_CAC_MARGIN_HEIGHT,
+		.field = V4L2_FIELD_NONE,
+	};
 
 	format = v4l2_subdev_get_try_format(sd, fh->pad, FIMC_ISP_SD_PAD_SINK);
-
-	fmt.colorspace = V4L2_COLORSPACE_SRGB;
-	fmt.code = fimc_isp_formats[0].mbus_code;
-	fmt.width = DEFAULT_PREVIEW_STILL_WIDTH + FIMC_ISP_CAC_MARGIN_WIDTH;
-	fmt.height = DEFAULT_PREVIEW_STILL_HEIGHT + FIMC_ISP_CAC_MARGIN_HEIGHT;
-	fmt.field = V4L2_FIELD_NONE;
 	*format = fmt;
 
 	format = v4l2_subdev_get_try_format(sd, fh->pad, FIMC_ISP_SD_PAD_SRC_FIFO);