USB: gadget: remove unneeded MODULE_VERSION() usage

MODULE_VERSION is useless for in-kernel drivers, so just remove all
usage of it in the USB gadget drivers.  Along with this, some
DRIVER_VERSION macros were removed as they are also pointless.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>