ARM: dts: stm32: fix warnings on stm32f469-disco board

Several warnings appear when building and checking stm32f429 device-tree:

arch/arm/boot/dts/stm32f469-disco.dts:182.28-184.5: Warning (unit_address_vs_reg): /soc/display-controller@40016800/port/endpoint@0: node has a unit name, but no reg or ranges property

.../arch/arm/boot/dts/stm32f469-disco.dtb: dsi@40016c00: Unevaluated properties are not allowed ('panel-dsi@0' was unexpected)
	From schema: .../Documentation/devicetree/bindings/display/st,stm32-dsi.yaml

Fix those.

Signed-off-by: Raphael Gallais-Pou <raphael.gallais-pou@foss.st.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Alexandre Torgue <alexandre.torgue@foss.st.com>