megaraid_sas: disable interrupt_mask before enabling hardware interrupts

Update driver "mask_interrupts" before enable/disable hardware interrupt
in order to avoid missing interrupts because of "mask_interrupts" still
set to 1 and hardware interrupts are enabled.

Cc: <stable@vger.kernel.org>
Signed-off-by: NSumit Saxena <sumit.saxena@avagotech.com>
Signed-off-by: NChaitra Basappa <chaitra.basappa@avagotech.com>
Reviewed-by: NMartin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: NChristoph Hellwig <hch@lst.de>

drivers/scsi/megaraid/megaraid_sas_fusion.c

@@ -102,6 +102,8 @@ megasas_enable_intr_fusion(struct megasas_instance *instance)
 {
 	struct megasas_register_set __iomem *regs;
 	regs = instance->reg_set;
+
+	instance->mask_interrupts = 0;
 	/* For Thunderbolt/Invader also clear intr on enable */
 	writel(~0, &regs->outbound_intr_status);
 	readl(&regs->outbound_intr_status);
@@ -110,7 +112,6 @@ megasas_enable_intr_fusion(struct megasas_instance *instance)
 
 	/* Dummy readl to force pci flush */
 	readl(&regs->outbound_intr_mask);
-	instance->mask_interrupts = 0;
 }
 
 /**