usb: cdns3: Refactoring names in reusable code

Patch change the functions and objects names in reusable code.
The reusable code includes core.c, core.h, drd.c and drd.h files.
It also changes the names of all references to these functions and
objects in other cdns3 files. There are a lot of changes, but all
changes are very trivial.
The reason of this patch is to avoid of mixing prefix cdns3 and cdnsp in
in cdnsp driver what could introduce some confusion in understanding
of cdnsp driver.
This patch assumes to use three different prefixes in Cadence
USB drivers:
  cdns: for common reusable code
  cdnsp: for names related only with cdnsp driver
  cdns3: for names related only with cdns3 driver

Signed-off-by: Pawel Laszczak <pawell@cadence.com>
Tested-by: Aswath Govindraju <a-govindraju@ti.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>