tg3: Add code to verify RODATA checksum of VPD

This patch adds code to verify the checksum stored in the "RV" info
keyword of the RODATA VPD section.

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