tg3: Fix the setting of the APE_HAS_NCSI flag

The driver currently skips setting this flag if the VPD contains the
firmware version string.  We fix this by separating the probing of NCSI
from the reading of the NCSI version string.  The APE_HAS_NCSI flag is
needed to properly read sensor data.

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