[SCSI] mvsas: misc improvements

Change code to match HBA datasheet.
Change code to make it readable.
Add support big endian for mvs_prd_imt.
Add cpu_to_le32 and cpu_to_le64 to use on addr.
Add scan_finished for structure mvs_prv_info.

Signed-off-by: Xiangliang Yu <yuxiangl@marvell.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>