tests: drivers: spi: spi_loopback: update spi_loopback test

- add nucleo_c071rb overlay file to setup spi and dma nodes

- Add the nucleo_c071rb configuration file to reduce the size of
SPI_LARGE_BUFFER_SIZE to avoid RAM overflow and be able
to run the test.

- update testcase.yaml for CI integration

Signed-off-by: Fabrice DJIATSA <fabrice.djiatsa-ext@st.com>

Author: djiatsaf-st

tests/drivers/spi/spi_loopback/boards/nucleo_c071rb.conf

@@ -0,0 +1 @@
+CONFIG_SPI_LARGE_BUFFER_SIZE=8000

tests/drivers/spi/spi_loopback/boards/nucleo_c071rb.overlay

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2025 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&spi1 {
+	dmas = <&dmamux1 2 17 (STM32_DMA_PERIPH_TX | STM32_DMA_PRIORITY_HIGH)
+		&dmamux1 1 16 (STM32_DMA_PERIPH_RX | STM32_DMA_PRIORITY_HIGH)>;
+	dma-names = "tx", "rx";
+	slow@0 {
+		compatible = "test-spi-loopback-slow";
+		reg = <0>;
+		spi-max-frequency = <500000>;
+	};
+	fast@0 {
+		compatible = "test-spi-loopback-fast";
+		reg = <0>;
+		spi-max-frequency = <16000000>;
+	};
+};
+
+&dma1 {
+	status = "okay";
+};
+
+&dmamux1 {
+	status = "okay";
+};

tests/drivers/spi/spi_loopback/testcase.yaml

@@ -65,6 +65,7 @@ tests:
     extra_args: EXTRA_CONF_FILE="overlay-stm32-spi-dma.conf"
     platform_allow:
       - b_u585i_iot02a
+      - nucleo_c071rb
       - nucleo_g474re
       - nucleo_f207zg
       - nucleo_f429zi
@@ -120,6 +121,7 @@ tests:
     extra_args: EXTRA_CONF_FILE="overlay-stm32-spi-interrupt.conf"
     platform_allow:
       - b_u585i_iot02a
+      - nucleo_c071rb
       - nucleo_f207zg
       - nucleo_f429zi
       - nucleo_f746zg