All PF mailbox events are conveyed through a common interrupt
(vector 0). This interrupt vector is shared by reset and mailbox.

This patch adds the handling of mailbox interrupt event and its
deferred processing in context to a separate mailbox task.
Signed-off-by: NSalil Mehta <salil.mehta@huawei.com>
Signed-off-by: Nlipeng <lipeng321@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>