usb: phy: am335x: fix race condition in _probe

power off the phy should be done before populate the phy. Otherwise,
am335x_init() could be called by the phy owner to power on the phy first,
then am335x_phy_probe() turns off the phy again without the caller knowing
it.

Fixes: 2fc711d7 ("usb: phy: am335x: Enable USB remote wakeup using PHY wakeup")
Cc: stable@vger.kernel.org # v3.18+
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>