usb: dwc3: gadget: no more tracking endpoint type with its name

I really thought this would be useful, but as it
turns out, it creates more problems than fixes. The
amount of times we had to fix this because some
other commit shuffled things around and ended up
regressing this tiny little string manupulation...

Might as well remove it, since it has a negligible
added benefit.

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