[BNX2]: Fix netdev watchdog on 5708.

There's a bug in the driver that only initializes half of the context
memory on the 5708.  Surprisingly, this works most of the time except
for some occasional netdev watchdogs when sending a lot of 64-byte
packets.  The fix is to add the missing code to initialize the 2nd
halves of all context memory.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Acked-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>