usb: dwc3: core: fix incorrect usage of resource pointer

Populate the resources for xhci afresh instead of directly using the
*struct resource* of core. *resource* structure has parent, sibling,
child pointers which should be filled only by resource API's. By
directly using the *resource* pointer of core in xhci, these parent,
sibling, child pointers are already populated even before
*platform_device_add* causing side effects.

Cc: stable@vger.kernel.org # v3.4, v3.5
Reported-by: Ruchika Kharwar <ruchika@ti.com>
Tested-by: Moiz Sonasath <m-sonasath@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>