Since mac_init is too heavy to be called when the link changes,
moved the speed_set configuration to a new function and added
mac_ops->set_speed function pointer.  This function will be
called from adjust_link callback.

Added cases for 10/100 support for SGMII based 1G interface.
Signed-off-by: NIyappan Subramanian <isubramanian@apm.com>
Tested-by: NFushen Chen <fchen@apm.com>
Tested-by: NToan Le <toanle@apm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>