scsi: mpt3sas: Fix sync irqs

scsi: mpt3sas: Fix sync irqs

_base_process_reply_queue() called from _base_interrupt() may schedule a
new irq poll. Fix this by calling synchronize_irq() first.

Also ensure that enable_irq() is called only when necessary to avoid
"Unbalanced enable for IRQ..." errors.

Link: https://lore.kernel.org/r/20200910142126.8147-1-thenzl@redhat.com
Fixes: 4cd814209be0 ("scsi: mpt3sas: Irq poll to avoid CPU hard lockups")
Acked-by: Sreekanth Reddy <sreekanth.reddy@broadcom.com>
Signed-off-by: Tomas Henzl <thenzl@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>