usb: gadget: f_qdss: Update usb string table based on channel name

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

Change-Id: I9787b1bc5f56f1f7d489ab27cbb9437ffaec3541
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>