usb: gadget: f_qdss: Update usb string table based on gadget transport

Currently driver is passing generic string as part of string descriptor
for all supported transports. Instead pass transport specific string
because USB host may represent the enumerated device using string passed
in usb string descriptor.

Change-Id: I16c0aa82a62f5a0ccbc61aeea316053b3cb18022
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>