tg3: Add support for selfboot format 1 v6

5718 B0 and 5719 devices will use a new selfboot firmware format.  This
patch adds code to detect the new format so that bootcode versions get
reported correctly.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>