usb: gadget: storage: add superspeed support

this patch adds superspeed descriptors for the
storage gadgets.

Acked-by: Michal Nazarewicz <mina86@mina86.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --cc drivers/usb/gadget/f_mass_storage.c
Simple merge

diff --cc drivers/usb/gadget/file_storage.c
Simple merge

diff --cc drivers/usb/gadget/mass_storage.c
Simple merge

diff --cc drivers/usb/gadget/storage_common.c
Simple merge