arm64: dts: imx8mp: Switch to DT overlays for i.MX8MP DHCOM SoM

Add DT overlays to support additional DH i.MX8MP DHCOM SoM 660-100
population options with 1x or 2x RMII PHY mounted on PDK2 or PDK3
carrier boards.

Use SPL DTO support to apply matching SoM specific DTO to cater
for the SoM differences. Remove ad-hoc patching of control DT from
fdtdec_board_setup().

Signed-off-by: Marek Vasut <marex@denx.de>
diff --git a/arch/arm/dts/Makefile b/arch/arm/dts/Makefile
index 60e9271..50bdb29 100644
--- a/arch/arm/dts/Makefile
+++ b/arch/arm/dts/Makefile
@@ -1064,6 +1064,9 @@
 	imx8mq-phanbell.dtb \
 	imx8mp-beacon-kit.dtb \
 	imx8mp-data-modul-edm-sbc.dtb \
+	imx8mp-dhcom-som-overlay-eth1xfast.dtbo \
+	imx8mp-dhcom-som-overlay-eth2xfast.dtbo \
+	imx8mp-dhcom-pdk-overlay-eth2xfast.dtbo \
 	imx8mp-dhcom-pdk2.dtb \
 	imx8mp-dhcom-pdk3.dtb \
 	imx8mp-evk.dtb \