Auto power-down (APD) support is a power-saving feature. It should be
selectively enabled since it might expose MAC bugs. This patch changes
the code to enable APD only if the PHY_BRCM_AUTO_PWRDWN_ENABLE flag is
set. The tg3 driver was changed to set this bit.
Signed-off-by: Matt Carlson <mcarlson@broadcom.com> Reviewed-by: Michael Chan <mchan@broadcom.com> Signed-off-by: David S. Miller <davem@davemloft.net>