[media] s5p-mfc: Set DMA_ATTR_ALLOC_SINGLE_PAGES

We do video allocation all the time and we need it to be fast.  Plus TLB
efficiency isn't terribly important for video.

That means we want to set DMA_ATTR_ALLOC_SINGLE_PAGES.

See also the previous change (commit 14d3ae2e "ARM: dma-mapping: Use
DMA_ATTR_ALLOC_SINGLE_PAGES hint to optimize allocation").

[m.szyprowski: rebased patch onto v4.9-rc1 and adapted changes
 to latest videbuf2 changes, this simplifies code changes to
 only set proper dma attribute flag and comment the reason
 for it, added commit id of arch/arm/mm patch]

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>