usb: dwc3: core: make dwc3_set_mode() work properly

We can't have both Host and Peripheral roles active at the same time
because of one detail on DWC3: it shares the same memory area for both
Host and Peripheral registers.

When swapping roles we must reinitialize the new role every
time. Let's make sure this works for our debugfs interface.

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