drm/exynos: Fix multiplatform breakage for ipp/gsc

There is no need to include "plat/map-base.h" in ipp driver. Remove
this and enable this driver for multi-platform.

However gsc driver is not multiplatform compliant yet, so make the
compilation conditional upon !ARCH_MULTIPLATFORM.

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>