net/mlx4_core: Avoid failing the interrupts test

Test interrupts fails if not all completion vectors called
request_irq. This case happens if only mlx4_en is loaded and
we have more completion vectors than rx rings.

Fixes: c66fa19c ('net/mlx4: Add EQ pool')
Signed-off-by: Carol L Soto <clsoto@linux.vnet.ibm.com>
Acked-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>