swiotlb: search and replace "int dir" with "enum dma_data_direction dir"

.. to catch anybody doing something funky.

See "swiotlb: swiotlb: add swiotlb_tbl_map_single library function" for
full description of patchset.

[v2: swiotlb_sync_single_range_* no more - removed usage]
[v3: enum dma_data_direction direction -> enum dma_data_direction dir]

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Tested-by: Albert Herranz <albert_herranz@yahoo.es>