[SCSI] ipr: Faster sg list fetch

Improve overall command performance by embedding the scatterlist
in the command block used by the adapter. This decreases
the overall number of DMAs required for a single command.

Signed-off-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>