usb: dwc3-msm: Add usb_ep_autoconfig_by_name

Add a helper function which a function driver such as f_gsi can
use to choose an endpoint by name, eg ep1in-gsi.

Change-Id: Id9fd42e423cb1c99c7c98a761dec0cd8bf150b82
Signed-off-by: Jack Pham <jackp@codeaurora.org>