usb-hid: Increase MAX_KBD_EVENT

Some USB keyboards use max packet sizes beyond the current maximum
supported by SeaBIOS.

This increases the available size to support keyboards such as the
Matias Ergo Pro.

Signed-off-by: Stefan Ott <stefan@ott.net>
diff --git a/src/hw/usb-hid.c b/src/hw/usb-hid.c
index a22765b..92c6b19 100644
--- a/src/hw/usb-hid.c
+++ b/src/hw/usb-hid.c
@@ -56,7 +56,7 @@
     u8 keys[6];
 };
 
-#define MAX_KBD_EVENT 10
+#define MAX_KBD_EVENT 16
 
 static int
 usb_kbd_setup(struct usbdevice_s *usbdev