[SCSI] mvsas: Add support for interrupt tasklet

Add support for interrupt tasklet, which will improve performance.
Correct spelling of "20011"

[jejb: simplified ifdefs and fixed unused variable problem]
Signed-off-by: Xiangliang Yu <yuxiangl@marvell.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>