[SCSI] advansys: convert to use the data buffer accessors

- remove the unnecessary map_single path.
- convert to use the new accessors for the sg lists and the parameters.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

- convert the statistics to not distinguish between single and sg xfers
- replace ASC_CEILING with DIV_ROUND_UP
- remove an obsolete comment
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>