[SCSI] mvsas: fix 94xx hotplug issue

Fix 94xx A0/B0 revision hotplug issue.
Remove unused macro: DISABLE_HOTPLUG_DMA_FIX

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