media: s5p-mfc: replace custom reserved memory handling code with generic one

This patch removes custom code for initialization and handling of
reserved memory regions in s5p-mfc driver and replaces it with generic
reserved memory regions api.

s5p-mfc driver now handles two reserved memory regions defined by
generic reserved memory bindings. Support for non-dt platform has been
removed, because all supported platforms have been already converted to
device tree.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>