bnx2x: Link Flap Avoidance

Various flows in the bnx2x driver cause a link-flap - if the link
is up, it would be toggled down (after a mac/phy reset) and then
taken back up.

In many of these cases, there is no need to do cause such a flap,
as the associated flows should not actually affect the link.

This patch adds the 'Link Flap Avoidance' mechanism, which allows
the driver to better determine if a given flow requires a link change,
and thus minimize the number of link flaps caused by the driver.

Signed-off-by: Yaniv Rosner <yaniv.rosner@broadcom.com>
Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>