usb: otg: ab8500-usb: make probe() work again

The probe() function will always fail because we're testing the wrong
variable.

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