video: imx: Add LDB driver

video: imx: Add LDB driver

Add support for the LVDS Display Bridge (LDB) found on i.MX8MP.

When attached, the bridge driver looks for panels connected to one of
its two outputs and adapts its own configuration to use them. There is
currently no support for merged/split displays.

Note regarding the clock configuration:
The LDB output clock should be absolutely identical to the LCDIF output
clock so both blocks can talk to each other synchronously. However, the
LDB clock has an internal divisor of 7 (respectively 3.5 in dual
configuration) which means the LDB input clock must be explicitly set
once we know the configuration.

This driver was tested on i.MX8MP using a single panel connected to the
LVDS2 interface.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>