tg3: Detect APE enabled devs earlier

The following patch will require the driver to communicate with the APE
much sooner than before.  This patch make sure the APE registers are
memory mapped and that the ENABLE_APE bit is set before the first use.

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