[nrf fromlist] tests: drivers: spi: spi_loopback: Run test on nrf54h20 PPR XIP

The spi_loopback test requires more RAM than is avilable
on nrf54h20dk/nrf54h20/cpuppr target.

Meanwhile, test fits in Execute In Place (XIP) variant
of the PPR target.

Switch spi_loopback test to nrf54h20 PPR XIP target.

Upstream PR #: 96562

Signed-off-by: Sebastian Głąb <[email protected]>

Author: nordic-segl

tests/drivers/spi/spi_loopback/boards/nrf54h20dk_nrf54h20_cpuppr.overlay

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2024 Nordic Semiconductor ASA
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+#include "nrf54h20dk_nrf54h20_common.dtsi"
+
+&spi130 {
+	zephyr,pm-device-runtime-auto;
+	slow@0 {
+		compatible = "test-spi-loopback-slow";
+		reg = <0>;
+		spi-max-frequency = <DT_FREQ_K(500)>;
+	};
+	fast@0 {
+		compatible = "test-spi-loopback-fast";
+		reg = <0>;
+		spi-max-frequency = <DT_FREQ_M(8)>;
+	};
+};