Change the PFVF receipt flow on the VF side to read, ack and handle the
message instead of read, handle and ack.
This is done for (1) consistency with the PF side, see the function
adf_recv_and_handle_vf2pf_msg() in adf_pf2vf_msg.c, and (2) performance
reasons, to avoid keeping the CSR busy while parsing the message.

In addition, do not ACK PFVF legacy messages, as this driver is not
capable of handling PFVF legacy messages.
If a PFVF message with MSGORIGIN not set is received, do nothing.
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Marco Chiappero <marco.chiappero@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>