video: exynos: fimd: add support for various display color modes

Now fimd BPP color mode depends on vl_bpp value in struct "panel_info".

There is only 16BPP mode check, default mode is 24BPP.
Other fimd modes are usually unneeded and also needs some fimd driver
modifications and tests.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>