hpsa: generalize external arrays

External array LUNs must use target and lun numbers assigned by the
external array. So the driver must treat these differently from
local LUNs when assigning lun/target.

LUN's 'model' field has been used to detect Lun types that need
special treatment, but the desire is to eliminate the need to reference
specific array models, and support any external array.

Pass-through RAID (PTRAID) luns are not luns of the local controller,
so they are not reported in LUN count of command 'ID controller'.
However, they ARE reported in "Report logical Luns" command.
Local luns are listed first, then PTRAID LUNs.

The number of luns from "Report LUNs" in excess of those reported by
'ID controller' are therefore the PTRAID LUNS.

We can now remove function is_ext_target, and the 'white list'
array of supported model names.

Reviewed-by: Scott Teel <scott.teel@pmcs.com>
Reviewed-by: Justin Lindley <justin.lindley@pmcs.com>
Reviewed-by: Kevin Barnett <kevin.barnett@pmcs.com>
Signed-off-by: Don Brace <don.brace@pmcs.com>
Reviewed-by: Matthew R. Ochs <mrochs@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>