[media] s5p-tv: Add missing braces around sizeof in mixer_drv.c

Silences checkpatch warnings of type:
WARNING: sizeof mdev->res should be sizeof(mdev->res)
FILE: media/platform/s5p-tv/mixer_drv.c:301:
	memset(&mdev->res, 0, sizeof mdev->res);
WARNING: sizeof *mdev should be sizeof(*mdev)
FILE: media/platform/s5p-tv/mixer_drv.c:385:
	mdev = kzalloc(sizeof *mdev, GFP_KERNEL);

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Acked-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>