tests: subsys: sd: Add board overlays to support testcase

Add SD/EMMC overlay files to support testcases for Versal NET. This
overlays are used to select the device to be tested.

Signed-off-by: Paul Alvin <alvin.paulp@amd.com>

tests/subsys/sd/mmc/boards/versalnet_rpu.overlay

@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2025 Advanced Micro Devices, Inc. (AMD)
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	aliases {
+		sdhc0 = &sdhci1;
+	};
+};

tests/subsys/sd/sdmmc/boards/versalnet_rpu.overlay

@@ -0,0 +1,11 @@
+/*
+ * Copyright (c) 2025 Advanced Micro Devices, Inc. (AMD)
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	aliases {
+		sdhc0 = &sdhci0;
+	};
+};