usb: gadget: atmel: remove pointless retrieval of DT name property

The name is always non-NULL and then is not used anywhere in this function,
so remove it.

Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Felipe Balbi <balbi@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-usb@vger.kernel.org
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>