usb: dwc3: add dual role support using OTG block

This is useful on platforms (e.g. TI AM437x) that don't
have ID available on a GPIO but do have the OTG block.

We can obtain the ID state via the OTG block and use it
for dual-role switching.

Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>