Add support for the NorthWest Logic MIPI-DSI controller found
in the following i.MX8 platforms: i.MX8qm, i.MX8qxp and i.MX8mq.
This is the MIPI-DSI encoder containing the platform specific changes
and it uses the NWL MIPI-DSI bridge.
Currently only qm and qxp are tested with this driver. The mq support
will be added later.

Signed-off-by: Robert Chiras <robert.chiras@nxp.com>