ARM: dma-mapping: add support for CMA regions placed in highmem zone

This patch adds missing pieces to correctly support memory pages served
from CMA regions placed in high memory zones. Please note that the default
global CMA area is still put into lowmem and is limited by optional
architecture specific DMA zone. One can however put device specific CMA
regions in high memory zone to reduce lowmem usage.

Change-Id: I92ae4a772f24e0ca90c5560a826207850618b506
CRs-Fixed: 467034
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
[lauraa@codeaurora.org: Context fixups]
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>