usb: isp1760: Retrieve pdev memory resource from hcd at remove time

The platform driver remove function needs to release the memory resource
requested at probe time. Instead of retrieving the resource from the
platform device, retrieve it from the usb_hcd. This mimics the behaviour
of the PCI and OF glues, and will make it easier to share code between
all three glue layers.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>