[nrf fromlist] tests: drivers: spi: Add test cases for non standard frequencies.

Added test cases for nrf chips for non standard frequencies.

Upstream PR #: 92436

Signed-off-by: Michal Frankiewicz <michal.frankiewicz@nordicsemi.no>

Author: mif1-nordic

tests/drivers/spi/spi_controller_peripheral/boards/1m333333hz.overlay

@@ -0,0 +1,9 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&dut_spi_dt {
+	spi-max-frequency = <1333333>;
+};

tests/drivers/spi/spi_controller_peripheral/boards/2m666666hz.overlay

@@ -0,0 +1,9 @@
+/*
+ * Copyright (c) 2025 Nordic Semiconductor
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&dut_spi_dt {
+	spi-max-frequency = <2666666>;
+};

tests/drivers/spi/spi_controller_peripheral/testcase.yaml

@@ -45,6 +45,22 @@ tests:
     integration_platforms:
       - nrf52840dk/nrf52840
 
+  drivers.spi.spi_1M333333Hz:
+    extra_configs:
+      - CONFIG_TESTED_SPI_MODE=0
+    extra_args: EXTRA_DTC_OVERLAY_FILE="boards/1m333333hz.overlay"
+    integration_platforms:
+      - nrf54l15dk/nrf54l15/cpuapp
+      - nrf54h20dk/nrf54h20/cpuapp
+
+  drivers.spi.spi_2M666666Hz:
+    extra_configs:
+      - CONFIG_TESTED_SPI_MODE=0
+    extra_args: EXTRA_DTC_OVERLAY_FILE="boards/2m666666hz.overlay"
+    integration_platforms:
+      - nrf54l15dk/nrf54l15/cpuapp
+      - nrf54h20dk/nrf54h20/cpuapp
+
   drivers.spi.spi_4MHz:
     extra_configs:
       - CONFIG_TESTED_SPI_MODE=2