powerpc: Remove addr_needs_map in struct dma_mapping_ops

This patch adds max_direct_dma_addr to struct dev_archdata to remove
addr_needs_map in struct dma_mapping_ops. It also converts
dma_capable() to use max_direct_dma_addr.

max_direct_dma_addr is initialized in pci_dma_dev_setup_swiotlb(),
called via ppc_md.pci_dma_dev_setup hook.

For further information:
http://marc.info/?t=124719060200001&r=1&w=2

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Becky Bruce <beckyb@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>