fix: nrf54lm20dk matter-diagnostic-logs SRAM memory region overlap

Fix SRAM address mismatch in matter-diagnostic-logs snippet overlays that
caused 1024-byte overlap into memory beyond 511 KB cpuapp_sram boundary.
This corrupted UART driver state at runtime, rendering keyboard input
non-functional despite TX/logs continuing to print.

Shift DiagnosticLogMem from 0x2007DF40 to 0x2007DB40 to fit within actual
SRAM bounds. Affects nrf54lm20dk/nrf54lm20a/cpuapp and
nrf54lm20dk/nrf54lm20b/cpuapp targets used in Matter certification builds.

Signed-off-by: Michał Szablowski <michal.szablowski@nordicsemi.no>

Author: doublemis1

snippets/matter/matter-diagnostic-logs/boards/nrf54lm20dk_nrf54lm20a_cpuapp.overlay

@@ -4,9 +4,9 @@
  */
 
 / {
-	cpuapp_sram@2007df40 {
+	cpuapp_sram@2007db40 {
 		compatible = "zephyr,memory-region", "mmio-sram";
-		reg = <0x2007df40 0x20c0>;
+		reg = <0x2007db40 0x20c0>;
 		zephyr,memory-region = "DiagnosticLogMem";
 		status = "okay";
 
@@ -48,5 +48,5 @@
 
 /* Reduce cpuapp_sram usage by 8384 B to account for non-init area */
 &cpuapp_sram {
-	reg = <0x20000000 0x7df40>;
+	reg = <0x20000000 0x7db40>;
 };

snippets/matter/matter-diagnostic-logs/boards/nrf54lm20dk_nrf54lm20b_cpuapp.overlay

@@ -4,9 +4,9 @@
  */
 
 / {
-	cpuapp_sram@2007df40 {
+	cpuapp_sram@2007db40 {
 		compatible = "zephyr,memory-region", "mmio-sram";
-		reg = <0x2007df40 0x20c0>;
+		reg = <0x2007db40 0x20c0>;
 		zephyr,memory-region = "DiagnosticLogMem";
 		status = "okay";
 
@@ -48,5 +48,5 @@
 
 /* Reduce cpuapp_sram usage by 8384 B to account for non-init area */
 &cpuapp_sram {
-	reg = <0x20000000 0x7df40>;
+	reg = <0x20000000 0x7db40>;
 };