drm/exynos/fimc: replace hw access macros with functions

HW access macros implicitly depended on presence of ctx local variable.
This patch replaces them with C functions.

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

diff --cc drivers/gpu/drm/exynos/exynos_drm_fimc.c
Simple merge