media: exynos4-is: properly initialize frame format

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: 9a761e436843 ("[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>