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.