PowerPC: adapt for dma_map_ops changes

Adapt core PowerPC architecture code for dma_map_ops changes: replace
alloc/free_coherent with generic alloc/free methods.

Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
[added missing changes to arch/powerpc/kernel/vio.c]
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>