scsi: aacraid: Fix INTx/MSI-x issue with older controllers

commit 78cbccd3bd68 ("aacraid: Fix for KDUMP driver hang")

caused a problem on older controllers which do not support MSI-x (namely
ASR3405,ASR3805). This patch conditionalizes the previous patch to
controllers which support MSI-x

Cc: <stable@vger.kernel.org> # v4.7+
Fixes: 78cbccd3bd68 ("aacraid: Fix for KDUMP driver hang")
Reported-by: Arkadiusz Miskiewicz <a.miskiewicz@gmail.com>
Signed-off-by: Dave Carroll <david.carroll@microsemi.com>
Reviewed-by: Raghava Aditya Renukunta <RaghavaAditya.Renukunta@microsemi.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/aacraid/comminit.c

@@ -50,9 +50,13 @@ struct aac_common aac_config = {
 
 static inline int aac_is_msix_mode(struct aac_dev *dev)
 {
-	u32 status;
+	u32 status = 0;
 
-	status = src_readl(dev, MUnit.OMR);
+	if (dev->pdev->device == PMC_DEVICE_S6 ||
+		dev->pdev->device == PMC_DEVICE_S7 ||
+		dev->pdev->device == PMC_DEVICE_S8) {
+		status = src_readl(dev, MUnit.OMR);
+	}
 	return (status & AAC_INT_MODE_MSIX);
 }