usb: dwc3: pci: code cleanup

Removing a few items that are not needed anymore and
adding separate function for quirks.

Acked-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>