drm/exynos: support exynos5422 mipi-dsi

This patch supports mipi dsi for exynos5422. The dsi register
offsets of the exynos5422 are similar with exynos5433. However,
the values of the registers are quite different from the
exynos5433. For example, the exynos5422 uses sw reset like
previous chips.

Signed-off-by: Chanho Park <chanho61.park@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>