usb: dwc3: debug: add dwc3_gadget_event_type_string
usb: dwc3: debug: add dwc3_gadget_event_type_string

this new helper will return a pretty string for
DWC3 Gadget Events.

Signed-off-by: Felipe Balbi <94dddeeef08b001e003cce128ddc162a4e2c6cd2@ti.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs