hpsa: do not get enclosure info for external devices

Stop annoying "Error, could not get enclosure information"
messages.

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