[SCSI] simscsi: use sg buffer copy helper funcitons

This replaces simscsi_fillresult with scsi_sg_copy_from_buffer.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Tony Luck <tony.luck@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>