qlcnic: add interrupt diagnostic test

Interrupt test (offline) added in ethtool self test.
Register a temporary interrupt handler and then send command to fw
to raise an interrupt.

Signed-off-by: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: Amit Kumar Salecha <amit.salecha@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>