usb: dwc3: Set the max speed

Set the gadget's max speed coressponding to the core's max speed.

Change-Id: I4800ab716bf2d4797ad77169d99fc253d581d8f9
Signed-off-by: Devin Kim <dojip.kim@lge.com>
Reduce min capture period size from 320 to 64

Change-Id: I8d6ed9d06e49561e9a9db51940b997f321a1ae87