enetc: Add vf to pf messaging support

VSIs (VFs) may send a message to the PSI (PF) for general notification
or to gain access to hardware resources which requires host inspection.
These messages may vary in size and are handled as a partition copy
between two memory regions owned by the respective participants.
The PSI will respond with fail or success and a 16-bit message code.
The patch implements the vf to pf messaging mechanism above and, as the
first application making use of this support, it enables the VF to
configure its own primary MAC address.

Signed-off-by: Catalin Horghidan <catalin.horghidan@nxp.com>
Signed-off-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>