Add defines and documentation for enabling flow control on the stmmac. Flow
control was not implemented correctly on the stmmac driver and is currently
non-functional as a result. This is the first in a series of small patches
to correctly implement this feature.
Signed-off-by: Vince Bridgers <vbridger@opensource.altera.com>
Signed-off-by: David S. Miller <davem@davemloft.net>