dt-bindings: mfd: Add bindings for SAM9X75 LCD controller

dt-bindings: mfd: Add bindings for SAM9X75 LCD controller

Add new compatible string for the XLCD controller on sam9x75 variant
of the SAM9X7 SoC family.
The XLCD controller in sam9x75 variant supports interfacing with
LVDS and MIPI-DSI and parallel port RGB.

Signed-off-by: Manikandan Muralidharan <manikandan.m@microchip.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230712024017.218921-2-manikandan.m@microchip.com
Signed-off-by: Lee Jones <lee@kernel.org>