tg3: Restrict ASPM workaround devlist

The ASPM workaround setting obtained from NVRAM only works with devices
older than 5717.  This patch enforces the restriction.

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