usb: dwc3: shorten long delay in dwc3_gadget_set_link_state()

The loop in dwc3_gadget_set_link_state() was using a udelay(500),
which is a long time to delay in interrupt context. Change it to
udelay(5) and increase the loop count to match.

Signed-off-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>