drivers/fpga/Kconfig: fix build failure

drivers/fpga/Kconfig: fix build failure

While building m32r allmodconfig the build is failing with the error:

  ERROR: "bad_dma_ops" [drivers/fpga/zynq-fpga.ko] undefined!

Xilinx Zynq FPGA is using DMA but there was no dependency while
building.

Link: http://lkml.kernel.org/r/1464346526-13913-1-git-send-email-sudipm.mukherjee@gmail.com
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Acked-by: Moritz Fischer <moritz.fischer@ettus.com>
Cc: Alan Tull <atull@opensource.altera.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>