[SCSI] mvsas: correct bit map usage

Utilize DECLARE_BITMAP to define the tags array.

Signed-off-by: Ying Chu <jasonchu@marvell.com>
Signed-off-by: Andy Yan <ayan@marvell.com>
Signed-off-by: Ke Wei <kewei@marvell.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>