app: Fix DTS for Thingy:91x

- Add missing b0 and mcuboot overlays

- Set the secure size correctly for overlay-trace-backend.overlay

- Disable carrier for Thingy:91x. It would need it's own overlay as
the storage_partition is in external flash.

Signed-off-by: Markus Lassila <markus.lassila@nordicsemi.no>

Author: MarkusLassila

app/overlay-trace-backend.overlay

@@ -17,10 +17,15 @@
  *   0x2000_c800  Application RAM            ( 206 kB)
  */
 
+/delete-node/ &sram0_s;
 /delete-node/ &sram0_ns;
 
 &sram0 {
 
+	sram0_s: sram@0 {
+		reg = <0x0 0x4000>;
+	};
+
 	sram0_ns: sram@4000 {
 		reg = <0x4000 0x3c000>;
 		#address-cells = <1>;

app/sample.yaml

@@ -159,7 +159,6 @@ tests:
       - EXTRA_DTC_OVERLAY_FILE="overlay-carrier.overlay"
     platform_allow:
       - nrf9151dk/nrf9151/ns
-      - thingy91x/nrf9151/ns
     integration_platforms:
       - nrf9151dk/nrf9151/ns
   serial_modem.lwm2m_carrier.softbank:

app/sysbuild/b0/boards/thingy91x_nrf9151.overlay

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2026 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/ {
+	chosen {
+		zephyr,code-partition = &b0_partition;
+		zephyr,console = &uart1;
+	};
+};
+
+&uart1 {
+	current-speed = <1000000>;
+	status = "okay";
+};

app/sysbuild/mcuboot/boards/thingy91x_nrf9151.overlay

@@ -1,4 +1,17 @@
-&uart0 {
+/*
+ * Copyright (c) 2026 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
+ */
+
+/ {
+	chosen {
+		zephyr,code-partition = &s0_partition;
+		zephyr,console = &uart1;
+	};
+};
+
+&uart1 {
+	current-speed = <1000000>;
 	status = "okay";
-	current-speed = < 1000000 >;
 };