arm64: dts: ti: fix missing root overlay nodes and FIT config

When overlay dtsi files specify root nodes using the standard '/ {'
syntax within a '/plugin/' context, the dtc compiler orphans these
nodes. At runtime, the applied overlays lose critical bindings like
voltage regulators and CPU configuration, leading to SDHCI register
storms and clock initialization failures.

Target the root node explicitly via '&{/} {' to ensure correct overlay
application. Additionally, add all board-specific overlays to the
default FIT configuration to streamline automatic booting.

Signed-off-by: Heinrich Toews <ht@twx-software.de>

arch/arm64/boot/dts/ti/fitImage.its

@@ -74,7 +74,7 @@
         conf-750-8400 {
             description = "Boot Linux kernel with base FDT and overlays";
             kernel = "kernel";
-            fdt = "fdt-750-8400";
+            fdt = "fdt-750-8400", "img-overlay-750-8400-wosm-p0000042", "img-overlay-750-8400-base-p0000017", "img-overlay-750-8400-localbus-p0000007", "img-overlay-750-8400-interaction-p0000031";
         };
 
         overlay-750-8400-wosm-p0000042 {

arch/arm64/boot/dts/ti/k3-am623-pfc-750-84xx-interaction.dtsi

@@ -291,7 +291,7 @@
  * Group triplets from PCA9552 into multicolor LEDs to enable
  * led-class-multicolor and pattern trigger RGB support.
  */
-/ {
+&{/} {
 	sys_led: sys-led {
 		compatible = "leds-group-multicolor";
 		label = "sys";

arch/arm64/boot/dts/ti/k3-am623-pfc-750-84xx-kbus.dtsi

@@ -8,7 +8,7 @@
 
 #include "k3-am623-pfc-kbus.dtsi"
 
-/ {
+&{/} {
 	/* this name of the gpio-keys device is a
 	 * historical heritage from 3.6.11 kernel.
 	 * the device-name is checked in omsd. So we

arch/arm64/boot/dts/ti/k3-am623-pfc-750-84xx-wosm.dtsi

@@ -8,7 +8,7 @@
 
 
 
-/ {
+&{/} {
 	compatible = "ti,am623-pfc", "ti,am625";
 
 	cpus {