samples: accel_trig: add dts trigger mode for unsupport platform

mimxrt1040_evk and twr_ke18f need board rework for trigger mode
so dts need changed to add gpio trigger

fixes: #85444

Signed-off-by: Hake Huang <hake.huang@oss.nxp.com>

samples/sensor/accel_trig/boards/mimxrt1040_evk.overlay

@@ -0,0 +1,12 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright 2025 NXP
+ */
+
+
+&fxls8974 {
+	status = "okay";
+	int1-gpios = <&gpio1 11 GPIO_ACTIVE_LOW>;
+	int2-gpios = <&gpio1 12 GPIO_ACTIVE_LOW>;
+};

samples/sensor/accel_trig/boards/twr_ke18f.overlay

@@ -0,0 +1,11 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Copyright 2025 NXP
+ */
+
+&fxos8700 {
+	status = "okay";
+	int1-gpios = <&gpioa 14 GPIO_ACTIVE_LOW>;
+	int2-gpios = <&gpioa 17 GPIO_ACTIVE_LOW>;
+};