ARM: dma-mapping: remove custom consistent dma region

This patch changes dma-mapping subsystem to use generic vmalloc areas
for all consistent dma allocations. This increases the total size limit
of the consistent allocations and removes platform hacks and a lot of
duplicated code.

Atomic allocations are served from special pool preallocated on boot,
because vmalloc areas cannot be reliably created in atomic context.

Change-Id: Ibb2230e80249598a81122083bf3fa2f050a0a71e
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Git-commit: e9da6e9905e639b0f842a244bc770b48ad0523e9
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
[lauraa@codeaurora.org: Context fixups and tweaking of some prototypes]
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
dma-mapping.c: revert to ARM: dma-mapping: remove custom consistent dma region