drm/exynos: Add driver for Exynos Scaler module

Exynos Scaler is a hardware module, which processes graphic data fetched
from memory and transfers the resultant dato another memory buffer.
Graphics data can be up/down-scaled, rotated, flipped and converted color
space. Scaler hardware modules are a part of Exynos5420 and newer Exynos
SoCs.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Inki Dae <inki.dae@samsung.com>