swiotlb: add the swiotlb initialization function with iotlb memory

This enables the caller to initialize swiotlb with its own iotlb
memory.

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

[v2: changed ..with_tlb to ..with_tbl]

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