This patch enables six external event channels and one periodic output.
One GPIO is reserved for synchronizing multiple PHYs. The assignment
of GPIO functions can be changed via a module parameter.

The code supports multiple simultaneous events by inducing a PTP clock
event for every channel marked in the PHY's extended status word.
Signed-off-by: Richard Cochran <richard.cochran@omicron.at>
Signed-off-by: David S. Miller <davem@davemloft.net>