fsl/fman: enable FMan Keygen

Add support for the FMan Keygen with a hardcoded scheme to spread
incoming traffic on a FQ range based on source and destination IPs
and ports.

Signed-off-by: Iordache Florinel <florinel.iordache@nxp.com>
Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>