drivers: mipi_dbi: add support for DBI color coding

Add new configuration item color_coding in the structure
mipi_dbi_config and in mipi-dbi-device binding property.
The color coding is defined by MIPI Alliance Standard for
Display Bus Interface v2.0, which is required by some display
controllers and device.

Signed-off-by: Kate Wang <yumeng.wang@nxp.com>