MAINTAINERS: Add driver-api/fpga path

Add Documentation/driver-api/fpga path to MAINTAINERS file
for fpga.
Signed-off-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -5577,6 +5577,7 @@ S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/atull/linux-fpga.git
 Q:	http://patchwork.kernel.org/project/linux-fpga/list/
 F:	Documentation/fpga/
+F:	Documentation/driver-api/fpga/
 F:	Documentation/devicetree/bindings/fpga/
 F:	drivers/fpga/
 F:	include/linux/fpga/