scsi: megaraid_sas: Enable msix_load_balance for Invader and later controllers

Load balancing IO completions across all available MSI-X vectors should be
enabled for Invader and later generation controllers only.  This needs to
be disabled for older controllers.  Add an adapter type check before
setting msix_load_balance flag.

Fixes: 1d15d909 ("scsi: megaraid_sas: Load balance completions across all MSI-X")
Signed-off-by: Shivasharan S <shivasharan.srikanteshwara@broadcom.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>