x86: qemu: Imply virtio PCI transport and device drivers

Add virtio drivers for QEMU x86 targets.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

board/emulation/qemu-x86/Kconfig

@@ -21,5 +21,8 @@ config BOARD_SPECIFIC_OPTIONS # dummy
 	select X86_RESET_VECTOR
 	select QEMU
 	select BOARD_ROMSIZE_KB_1024
+	imply VIRTIO_PCI
+	imply VIRTIO_NET
+	imply VIRTIO_BLK
 
 endif