media: s5p-mfc: Add variant data for MFC v7 hardware for Exynos 3250 SoC

Commit 5441e9da ("[media] s5p-mfc: Core support for MFC v7")
which adds mfc v7 support for Exynos3250 and use the same compatible
string as used by Exynos5240 but both the IPs are a bit different in
terms of IP clock.
Add variant driver data based on the new compatible string
"samsung,exynos3250-mfc" for Exynos3250 SoC.

Suggested-by: Alim Akhtar <alim.akhtar@samsung.com>
Fixes: 5441e9da ("[media] s5p-mfc: Core support for MFC v7")
Signed-off-by: Aakarsh Jain <aakarsh.jain@samsung.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>