Add IBM ServeRAID M5110 to the hardware list.
This is a rebranded MegaRAID SAS 2208 [Thunderbolt] found e.g. on x3550 M4.

Reported by:	Ilia Noskov <noskov@nic.ru>
MFC after:	3 days
Include sys/systm.h after sys/param.h.

Suggested by:	pluknet
Fix an argument reversal in calls to scsi_read_element_status().

Reported by:	Ulrich Spoerlein <uqs@FreeBSD.org>
MFC after:	3 days
Make some improvements to r253322 to really rescan target, not a bus.
Add there and in two more places checks for NULL on xpt_alloc_ccb_nowait().