bnx2x: congestion management re-organization

The congestion management code has migrated into a common location,
allowing all fw writes controlling mf congestion to be made in a
single function in the code. This is a semantic change.

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>