be2net: use eq-id to calculate cev-isr reg offset

cev-isr reg offset for each function is better calculated using (any) eq-id
alloted to that function instead of using pci-func number(which
does not work in some configurations...)

Signed-off-by: Sathya Perla <sathyap@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>