USB: gadget: udc: Remove redundant license text

Now that the SPDX tag is in all USB files, that identifies the license
in a specific and legally-defined manner.  So the extra GPL text wording
can be removed as it is no longer needed at all.

This is done on a quest to remove the 700+ different ways that files in
the kernel describe the GPL license text.  And there's unneeded stuff
like the address (sometimes incorrect) for the FSF which is never
needed.

No copyright headers or other non-license-description text was removed.

Cc: Kevin Cernekee <cernekee@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Vladimir Zapolskiy <vz@mleia.com>
Cc: Sylvain Lemieux <slemieux.tyco@gmail.com>
Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: "Sören Brinkmann" <soren.brinkmann@xilinx.com>
Cc: Raviteja Garimella <raviteja.garimella@broadcom.com>
Cc: Romain Perier <romain.perier@collabora.com>
Cc: Johan Hovold <johan@kernel.org>
Cc: Al Cooper <alcooperx@gmail.com>
Cc: Srinath Mannam <srinath.mannam@broadcom.com>
Cc: Roger Quadros <rogerq@ti.com>
Cc: Krzysztof Opasiak <k.opasiak@samsung.com>
Cc: Stefan Agner <stefan@agner.ch>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: "Felix Hädicke" <felixhaedicke@web.de>
Cc: Peter Chen <peter.chen@nxp.com>
Cc: Allen Pais <allen.lkml@gmail.com>
Cc: Yuyang Du <yuyang.du@intel.com>
Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Acked-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>