riscv: Move virtio scan to board_late_init()

When virtio_init() gets called from board_init() PCI isn't ready. Thus,
virtio-over-PCI (e.g. network interfaces) devices can't be detected and
used without additional `virtio scan` scan in the shell or a script.

Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

arch/riscv/Kconfig

@@ -22,6 +22,7 @@ config TARGET_OPENPITON_RISCV64
 
 config TARGET_QEMU_VIRT
 	bool "Support QEMU Virt Board"
+	select BOARD_LATE_INIT
 
 config TARGET_SIFIVE_UNLEASHED
 	bool "Support SiFive Unleashed Board"

board/emulation/qemu-riscv/qemu-riscv.c

@@ -31,12 +31,6 @@ int is_flash_available(void)
 
 int board_init(void)
 {
-	/*
-	 * Make sure virtio bus is enumerated so that peripherals
-	 * on the virtio bus can be discovered by their drivers
-	 */
-	virtio_init();
-
 	return 0;
 }
 
@@ -46,6 +40,12 @@ int board_late_init(void)
 	if (CONFIG_IS_ENABLED(USB_KEYBOARD))
 		usb_init();
 
+	/*
+	 * Make sure virtio bus is enumerated so that peripherals
+	 * on the virtio bus can be discovered by their drivers
+	 */
+	virtio_init();
+
 	return 0;
 }