Staging: rtl8712: fix an error test in start_drv_threads()

Testing for "if (IS_ERR(padapter->cmdThread) < 0)" doesn't make sense.
The kthread_run() function returns error pointers on error pointers on
error so it should just be "if (IS_ERR(padapter->cmdThread))".

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>