Revert "[nrf noup] zephyr/boards: fix nrf54l15pdk ext flash dts overlay"

This reverts commit 6f5d3ae.

Signed-off-by: Jamie McCrae <[email protected]>

Author: nordicjm

boot/zephyr/boards/nrf54l15pdk_nrf54l15_cpuapp_ext_flash.overlay

@@ -14,8 +14,7 @@
 
 /delete-node/ &storage_partition;
 
-&cpuapp_rram {
-	reg = < 0x0 DT_SIZE_K(1524) >;
+&rram0 {
 	partitions {
 		boot_partition: partition@0 {
 			label = "mcuboot";