fpga: fpga-region: Cleanup an outdated comment

Clean up an outdated comment claiming FPGA regions implement devicetree
support for reprogramming FPGAs.
Signed-off-by: Moritz Fischer <mdf@kernel.org>

drivers/fpga/fpga-region.c

 // SPDX-License-Identifier: GPL-2.0
 /*
- * FPGA Region - Device Tree support for FPGA programming under Linux
+ * FPGA Region - Support for FPGA programming under Linux
  *
  *  Copyright (C) 2013-2016 Altera Corporation
  *  Copyright (C) 2017 Intel Corporation