This patch converts dma_map_single and dma_unmap_single to use
map_page and unmap_page respectively and removes unnecessary
map_single and unmap_single in struct dma_mapping_ops.

This leaves intel-iommu's dma_map_single and dma_unmap_single since
IA64 uses them. They will be removed after the unification.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NIngo Molnar <mingo@elte.hu>