USB: phy: am335x-control: fix device and of_node leaks

Make sure to drop the references taken by of_parse_phandle() and
bus_find_device() before returning from am335x_get_phy_control().

Note that there is no guarantee that the devres-managed struct
phy_control will be valid for the lifetime of the sibling phy device
regardless of this change.

Fixes: 3bb869c8 ("usb: phy: Add AM335x PHY driver")
Acked-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>