drm/exynos: refactor driver and device registration code

This patch refactors driver and device registration by moving all drivers
to the common array. This way additional flags can be added later for
new features. #ifdef-based code has been replaced by IS_ENABLED() macro
usage.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>