microblaze: Wire CMA allocator

Based on commit 04e3543e228f ("microblaze: use the generic dma coherent
remap allocator")
CMA can be easily enabled by calling dma_contiguous_reserve() at the end of
mmu_init(). High limit is end of lowmem space which is completely unused at
this point of time.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 5f46ebe..e628929 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -27,6 +27,7 @@
 	select HAVE_ARCH_HASH
 	select HAVE_ARCH_KGDB
 	select HAVE_DEBUG_KMEMLEAK
+	select HAVE_DMA_CONTIGUOUS
 	select HAVE_DYNAMIC_FTRACE
 	select HAVE_FTRACE_MCOUNT_RECORD
 	select HAVE_FUNCTION_GRAPH_TRACER