scsi: iscsi: Use EFI GetVariable only when available

Replace the EFI runtime services check with one that tells us whether
EFI GetVariable() is implemented by the firmware.

Cc: "James E.J. Bottomley" <jejb@linux.ibm.com>
Cc: "Martin K. Petersen" <martin.petersen@oracle.com>
Cc: linux-scsi@vger.kernel.org
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

drivers/scsi/isci/init.c

@@ -621,7 +621,7 @@ static int isci_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
 		return -ENOMEM;
 	pci_set_drvdata(pdev, pci_info);
 
-	if (efi_enabled(EFI_RUNTIME_SERVICES))
+	if (efi_rt_services_supported(EFI_RT_SUPPORTED_GET_VARIABLE))
 		orom = isci_get_efi_var(pdev);
 
 	if (!orom)