tests: drivers: spi loopback running on stm32u585 disco kit

Configure the target board to PASS the test case.
The PCLK2 clock feeding the SPI1 is reduced by 2 (apb2 prescaler)
to accept the slow freq config.
The SPI1 MISO and MOSI pins are linked on the HW board
(on arduino CN13, D11 & D12)

Signed-off-by: Francois Ramu <[email protected]>

Author: FRASTM

tests/drivers/spi/spi_loopback/boards/b_u585i_iot02a.conf

@@ -0,0 +1,3 @@
+CONFIG_SPI_LOOPBACK_DRV_NAME="SPI_1"
+CONFIG_SPI_ASYNC=y
+CONFIG_SPI_LOOPBACK_MODE_LOOP=n

tests/drivers/spi/spi_loopback/boards/b_u585i_iot02a.overlay

@@ -0,0 +1,9 @@
+/*
+ * Copyright (c) 2021 STMicroelectronics
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&rcc {
+	apb2-prescaler = <2>;
+};