Input: powermate - fix use-after-free in powermate_config_complete

In the Linux kernel, the following vulnerability has been resolved:

Input: powermate - fix use-after-free in powermate_config_complete

syzbot has found a use-after-free bug [1] in the powermate driver. This

happens when the device is disconnected, which leads to a memory free from

the powermate_device struct. When an asynchronous control message

completes after the kfree and its callback is invoked, the lock does not

exist anymore and hence the bug.

Use usb_kill_urb() on pm->config to cancel any in-progress requests upon

device disconnection.

[1] https://syzkaller.appspot.com/bug?extid=0434ac83f907a1dbdd1e