bnx2x: Remove two prefetch()

1) Even on 64bit arches, sizeof(struct sk_buff) < 256
2) No need to prefetch same pointer twice.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Eilon Greenstein <eilong@broadcom.com>
Acked-by: Eliezer Tamir <eliezer@tamir.org.il>
Signed-off-by: David S. Miller <davem@davemloft.net>