hwmon: (powerz) Fix missing usb_kill_urb() on signal interrupt

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

hwmon: (powerz) Fix missing usb_kill_urb() on signal interrupt

wait_for_completion_interruptible_timeout() returns -ERESTARTSYS when

interrupted. This needs to abort the URB and return an error. No data

has been received from the device so any reads from the transfer

buffer are invalid.

The original code tests !ret, which only catches the timeout case (0).

On signal delivery (-ERESTARTSYS), !ret is false so the function skips

usb_kill_urb() and falls through to read from the unfilled transfer

buffer.

Fix by capturing the return value into a long (matching the function

return type) and handling signal (negative) and timeout (zero) cases

with separate checks that both call usb_kill_urb() before returning.