ui: use evdev keymap when running under wayland

Wayland always uses evdev as its input source, so QEMU
can use the existing evdev keymap data

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Tested-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20161201094117.16407-1-berrange@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>