ARM: EXYNOS: Remove code for MFC custom reserved memory handling

Once MFC driver has been converted to generic reserved memory bindings,
there is no need for custom memory reservation code.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>