mlxfw: Introduce status_notify op and call it to notify about the status

Add new op status_notify which is called to update the user about
flashing status.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>