usb: dwc3: Do not update the resource of platform device

commit <44feb8e6> ("usb: dwc3: use local copy of resource to
fix-up register offset") is adding a local variable to cache
local copy of memory resource. Hence there is no need to update
the resource variable and use the local copy of it.

Change-Id: Iad52fc39575cf177b7ee63e9404cc469b8c8cfa3
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>