MAINTAINERS: Add file patterns for fpga device tree bindings

Submitters of device tree binding documentation may forget to CC
the subsystem maintainer if this is missing.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Moritz Fischer <moritz.fischer@ettus.com>
Cc: Alan Tull <atull@opensource.altera.com>
Cc: Moritz Fischer <moritz.fischer@ettus.com>
Cc: linux-fpga@vger.kernel.org
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -5143,6 +5143,7 @@ R:	Moritz Fischer <moritz.fischer@ettus.com>
 L:	linux-fpga@vger.kernel.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/atull/linux-fpga.git
+F:	Documentation/devicetree/bindings/fpga/
 F:	drivers/fpga/
 F:	include/linux/fpga/fpga-mgr.h
 W:	http://www.rocketboards.org