[TG3]: Fix the polarity bit.

For most pre-5705 devices, multiple link interrupts were being generated
for a single physical link change.  The source of the interrupts was
determined to be unnecessary toggling of the MAC link polarity bit.

This patch changes the way the link polarity bit gets configured.  Where
possible, code that dynamically configures the bit in response to link
changes has been replaced by code that configures the bit once during
initialization time and then leaves the bit alone.

For correctness, this patch also limits the use of the bit to those
devices where it is defined, namely devices before the 5705.  This patch
also corrects the link polarity configurations for 5700 devices when
paired against a bcm5411 phy.

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>