arm64: Replace ZONE_DMA32 with ZONE_DMA

arm64: Replace ZONE_DMA32 with ZONE_DMA

On arm64 we do not have two DMA zones, so it does not make sense to
implement ZONE_DMA32. This patch changes ZONE_DMA32 with ZONE_DMA, the
latter covering 32-bit dma address space to honour GFP_DMA allocations.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
(cherry picked from commit 19e7640d1f2302c20df2733e3e3df49acb17189e)
Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Conflicts:
	arch/arm64/mm/dma-mapping.c
Signed-off-by: Mark Brown <broonie@linaro.org>