usb: Use DECLARE_USB_FUNCTION() for initializing USB QDSS function driver

USB QDSS function driver is already registered as module and having init
and exit APIs. DECLARE_USB_FUNCTION_INIT() adds additional module entries
for USB QDSS function driver. This results into seeing error as
"usb_qdss_init: failed to register diag -17" when usb_function_register()
is called 2nd time. Hence fix this issue by using DECLARE_USB_FUNCTION()
instead of DECLARE_USB_FUNCTION_INIT() API.

Change-Id: I37da484eaa44e60e331d18fa720289a2dff8ad50
Signed-off-by: Mayank Rana <mrana@codeaurora.org>