Refactor the PFVF receive logic so it is common between PF and VF and
make it device specific.

This is in preparation for the introduction of PFVF support in the
qat_4xxx driver since the receive logic differs between QAT GEN2 and
QAT GEN4 devices.
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Co-developed-by: Marco Chiappero <marco.chiappero@intel.com>
Signed-off-by: Marco Chiappero <marco.chiappero@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>