tg3: Add link state reporting to UMP firmware

All variants of the 5714, 5715, and 5780 offer a feature called the
"Universal Management Port".  This feature is implemented in firmware
and is largely transparent to the driver, except...

It turns out that the UMP firmware needs to know the current status
of the link.  Because the firmware cannot touch the PHY registers while
the driver is in control of the device, it needs the driver to report
link status changes through an additional handshaking mechanism.
Without this handshake, it has been observed in the field that the UMP
firmware will not operate correctly.

This patch implements the new handshake with the UMP firmware.  Since
the handshake uses the same mechanism ASF heartbeats use, code was
added to detect and wait for completion of a pending previous event.

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