usb: dwc3: initialize platform data at pci glue layer

This patch initializes platform data at pci glue layer, and SoCs x86-based
platform vendor is able to define their flags in platform data at bus glue
layer. Then do some independent behaviors at dwc3 core level.

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>