usb: Add DWC3 model

usb: Add DWC3 model

This patch adds skeleton model of dwc3 usb controller attached to
xhci-sysbus device. It defines global register space of DWC3 controller,
global registers control the AXI/AHB interfaces properties, external FIFO
support and event count support. All of which are unimplemented at
present,we are only supporting core reset and read of ID register.

Signed-off-by: Vikram Garhwal <fnu.vikram@xilinx.com>
Signed-off-by: Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Message-id: 1607023357-5096-3-git-send-email-sai.pavan.boddu@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>