arm: exynos: realign the code to allow support for newer 64-bit platforms

The existing Exynos 32-bit platform support needs to be realigned in
order to support newer 64-bit Exynos platforms. The driver model will
be utlized for drivers on the 64-bit Exynos platforms and so some of
the older platform support code would not be required for the newer
64-bit Exynos platforms.

Cc: Minkyu Kang <mk7.kang@samsung.com>
Signed-off-by: Thomas Abraham <thomas.ab@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>