usb: cdns3: Moves reusable code to separate module

Patch moves common reusable code used by cdns3 and cdnsp driver
to cdns-usb-common library. This library include core.c, drd.c
and host.c files.

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>