media: exynos-gsc: Add compatible for Exynos 5250 and 5420 SoC version

Exynos 5250 and 5420 have different hardware rotation limits.
Since we have to distinguish between these two, we add different
compatible: samsung,exynos5250-gsc and samsung,exynos5420-gsc.

Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>