drm/exynos: add exynos5420 support for fimd

This patch adds a exynos5420 driver data to support mic_bypass
option to bypass the mic from display out path.
The mic(Mobile image compressor) compresses RGB data from fimd
and send the compressed data to the mipi dsi.
The bypass option can be founded from system register and the bit
is 11. The option bit has been introduced since exynos5420. The
only difference between exynos5250 and exynos5420/exynos5422 is
existence of the bit. Until the MIC is defined and enabled from
device tree, the bypass mic will be default option.

Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>