bnx2x: access cfc_del_event only if the opcode is CFC_DEL

It's not really a bug, but it was odd that bnx2x_eq_int() read the
message data as if it were a cfc_del_event regardless of the event type.
It's cleaner to access only the appropriate member of union event_data
after checking the event opcode.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>