riscv: qemu: Enable usb keyboard as an input device

This brings PCI xHCI support to QEMU RISC-V and uses a usb keyboard
as one of the input devices.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Rick Chen <rick@andestech.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/include/configs/qemu-riscv.h b/include/configs/qemu-riscv.h
index d5146e7..584559c 100644
--- a/include/configs/qemu-riscv.h
+++ b/include/configs/qemu-riscv.h
@@ -17,7 +17,7 @@
 
 /* Environment options */
 
-#define CFG_STD_DEVICES_SETTINGS	"stdin=serial\0" \
+#define CFG_STD_DEVICES_SETTINGS	"stdin=serial,usbkbd\0" \
 					"stdout=serial,vidconsole\0" \
 					"stderr=serial,vidconsole\0"