f_qdss: Use USB QDSS string descriptor with USB QDSS interface descriptor

QDSS Data and QDSS Ctrl related string descriptors are defined but those
are not being advertised to Host. Hence update USB QDSS interface
descriptor with USB QDSS string descriptor. This helps some of host side
application to detect enuermated QDSS interface and allows IO with it.

Change-Id: I1ff141f1b52d867d70ecc8f23ac065639999c0f9
Signed-off-by: Mayank Rana <mrana@codeaurora.org>