backend/libinput: add timeout to wait for input devices
If wlroots starts up a bit too soon, it might be initialized before input devices. In this situation, wait for a bit instead of immediately erroring out, just like we do for KMS devices.
If wlroots starts up a bit too soon, it might be initialized before input devices. In this situation, wait for a bit instead of immediately erroring out, just like we do for KMS devices.