MAINTAINERS: Move linux-fpga tree to new location

Move the linux-fpga tree to new location at:
 git://git.kernel.org/pub/scm/linux/kernel/git/mdf/linux-fpga.git



Signed-off-by: Moritz Fischer <mdf@kernel.org>
Link: https://lore.kernel.org/r/20190725174517.10516-1-mdf@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>