net: cpsw: Add support for wake-on-lan for cpsw

Some phy's can be configured to enable wake on lan (e.g. at803x or marvell 88E1318S).
There is no way how to enable wol on CPSW with such connected phys. This patch
adds this support. It is provided by calling the phy's related code.

Tested on board with at8030x connected phy. Wol interrupt line is
connected to GPIO0 on am335x.

Signed-off-by: Matus Ujhelyi <ujhelyi.m@gmail.com>
Acked-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: David S. Miller <davem@davemloft.net>