samples: drivers: i2c: rtio_loopback: add nucleo_f401re/nucleo_h503rb

Add nucleo_f401re and nucleo_h503rb boards to rtio_loopback tests
on the I2C driver.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>

samples/drivers/i2c/rtio_loopback/boards/nucleo_f401re.overlay

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/* I2C bus pins are exposed on the ST morpho and Arduino headers.
+ *
+ *  Bus        SDA               SCL
+ *          Pin   Hdr         Pin   Hdr
+ *  i2c1    PB9   CN5:9       PB8   CN5:10
+ *  i2c3    PC9   CN10:1      PA8   CN9:8
+ *
+ * Short Pin PB9 to PC9, and PB8 to PA8, for the test to pass.
+ */
+
+/ {
+	aliases {
+		i2c-controller = &i2c1;
+		i2c-controller-target = &i2c3;
+	};
+};

samples/drivers/i2c/rtio_loopback/boards/nucleo_h503rb.overlay

@@ -0,0 +1,32 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/* I2C bus pins are exposed on the ST morpho and Arduino headers.
+ *
+ *  Bus        SDA                    SCL
+ *          Pin   Hdr              Pin   Hdr
+ *  i2c1    PB7   CN5:9            PB6   CN5:10/CN10:3
+ *  i2c2    PB4   CN9:6/CN10:27     PB5   CN9:5/CN10:29
+ *
+ * Short Pin PB7 to PB4, and PB6 to PB5, for the test to pass.
+ */
+
+/ {
+	aliases {
+		i2c-controller = &i2c1;
+		i2c-controller-target = &i2c2;
+	};
+};
+
+&i2c1 {
+	pinctrl-0 = <&i2c1_scl_pb6 &i2c1_sda_pb7>;
+	pinctrl-names = "default";
+	clock-frequency = <I2C_BITRATE_FAST>;
+	status = "okay";
+};
+
+&i2c2 {
+	pinctrl-0 = <&i2c2_scl_pb5 &i2c2_sda_pb4>;
+	pinctrl-names = "default";
+	clock-frequency = <I2C_BITRATE_FAST>;
+	status = "okay";
+};

samples/drivers/i2c/rtio_loopback/sample.yaml

@@ -16,4 +16,6 @@ tests:
       - nrf5340dk/nrf5340/cpuapp
       - nrf54l15dk/nrf54l15/cpuapp
       - nrf54h20dk/nrf54h20/cpuapp
+      - nucleo_f401re
+      - nucleo_h503rb
       - ophelia4ev/nrf54l15/cpuapp