Update the mipi_dsi_northwest driver to implement mipi dsi bridge interfaces
and register it as a bridge controller. Users can call bridge common interfaces
to access the northwest driver, don't need to call its private driver functions.

We also add a kconfig entry for this driver, the name is changed to
CONFIG_IMX_NORTHWEST_MIPI_DSI

Signed-off-by: Ye Li <ye.li@nxp.com>