ARM: dts: stm32: Enable LVDS panel on i.Core STM32MP1 EDIMM2.2

Engicam i.Core STM32MP1 EDIMM2.2 Starter Kit has plugged with
7" LVDS panel.

Engicam i.Core STM32MP1 SoM has SN65DSI84 DSI to LVDS bridge.

This patch adds a display pipeline to connect DSI to SN65DSI84
to 7" LVDS panel.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>