ARM: dma: Drop GFP_COMP for DMA-IOMMU memory allocations

dma_alloc_coherent wants to split pages after allocation in order to
reduce the memory footprint. This does not work well with GFP_COMP
pages, so drop this flag before allocation.

This patch is ported from arch/avr32
(commit 3611553ef985ef7c5863c8a94641738addd04cff).

Change-Id: I67eb2b15807c36c6a3ade95ee35bf5856d8e0e11
Signed-off-by: Hiroshi Doyu <hdoyu@nvidia.com>

Rebase-Id: Rf13a569ebe836d341cf4d9287ff4b4711dde85cc