tests: entropy: api: add overlay for VirtIO Entropy device

Add `boards/qemu_x86_64.overlay` and some config modification
for testing `virtio,entropy` device.

Signed-off-by: TOKITA Hiroshi <tokita.hiroshi@gmail.com>

tests/drivers/entropy/api/boards/qemu_x86_64.conf

@@ -0,0 +1,5 @@
+# Copyright (c) 2025 TOKITA Hiroshi
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_PCIE=y
+CONFIG_HEAP_MEM_POOL_SIZE=1024

tests/drivers/entropy/api/boards/qemu_x86_64.overlay

@@ -0,0 +1,27 @@
+/*
+ * Copyright (c) 2025 TOKITA Hiroshi
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/ {
+	chosen {
+		zephyr,entropy = &virtio_entropy;
+	};
+};
+
+&pcie0 {
+	virtio_pci: virtio_pci {
+		compatible = "virtio,pci";
+
+		device-id = <0x1005>;
+		vendor-id = <0x1af4>;
+
+		interrupts = <0xb 0x0 0x0>;
+		interrupt-parent = <&intc>;
+
+		virtio_entropy: virtio_entropy {
+			compatible = "virtio,device4";
+		};
+	};
+};

tests/drivers/entropy/api/testcase.yaml

@@ -24,3 +24,11 @@ tests:
       - driver
       - entropy
       - psa-crypto
+  drivers.entropy.virtio:
+    filter: CONFIG_ENTROPY_VIRTIO
+    extra_args:
+      - EXTRA_CONF_FILE=./virtio.conf
+    tags:
+      - driver
+      - entropy
+      - virtio

tests/drivers/entropy/api/virtio.conf

@@ -0,0 +1,4 @@
+# Copyright (c) 2025 TOKITA Hiroshi
+# SPDX-License-Identifier: Apache-2.0
+
+CONFIG_VIRTIO=y