- remove the unnecessary map_single path.

- convert to use the new accessors for the sg lists and the
parameters.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: NSumant Patro <sumant.patro@lsi.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>