usb: dwc3: move dwc3 device ID bitmap to core.c

if we want to support situations where we have
both SoC and PCIe versions of the IP on the same
platform, we need to have sequential numbers between
them, otherwise we will still have name collisions.

Because of that, we need to move dwc3_get/put_device_id()
to core.c and export that symbol to be used by glue
layers.

Signed-off-by: Felipe Balbi <balbi@ti.com>