usb: gadget: f_fs: Add support for SuperSpeed Mode

usb: gadget: f_fs: Add support for SuperSpeed Mode

Allow userspace to pass SuperSpeed descriptors and
handle them in the driver accordingly.
This change doesn't modify existing desc_header and thereby
keeps the ABI changes backward compatible i.e. existing
userspace drivers compiled with old header (functionfs.h)
would continue to work with the updated kernel.

Signed-off-by: Manu Gautam <mgautam@codeaurora.org>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
[backport from upstream commit 8d4e897bd0150fab594a871484e554472ee01452]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-id: I8d4e897bd0150fab594a871484e554472ee01452