tg3: Reduce UMP event collision window

tg3: Reduce UMP event collision window

The tg3 driver needs to submit a few phy register values to the UMP
firmware each time the link state changes.  Up until now, the driver
would wait for the previous event to complete, then proceed to gather
data through a series of phy accesses.  Since phy accesses are
relatively slow, it is possible for another thread to attempt to submit
its own event while the UMP code is still construction its message.

This patch seeks to minimize the collision window as much as possible by
preloading the phy data.

(cherry picked from commit b28f389d92114ecf1a7c99eb3865438543a1808b)
Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Joe Jin <joe.jin@oracle.com>