[SCSI] mvsas: convert from rough draft to working driver

Convert rough draft Marvell 6440 driver to a working driver.
Added support for SAS and SATA devices, hotplug, wide port, and expanders.
Signed-off-by: Ke Wei <kewei@marvell.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>