arm64: mm: reserve per-numa CMA to localize coherent dma buffers

Right now, smmu is using dma_alloc_coherent() to get memory to save queues
and tables. Typically, on ARM64 server, there is a default CMA located at
node0, which could be far away from node2, node3 etc.
with this patch, smmu will get memory from local numa node to save command
queues and page tables. that means dma_unmap latency will be shrunk much.
Meanwhile, when iommu.passthrough is on, device drivers which call dma_
alloc_coherent() will also get local memory and avoid the travel between
numa nodes.

Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>