Currently all the functions related to the activation of the PFVF
protocol, both on PF and VF, include the direction specific "vf2pf"
name.

Replace the existing naming schema with:
  - a direction agnostic naming, that applies to both PF and VF, for the
    function pointer ("pfvf")
  - a direction specific naming schema for the implementations ("pf2vf" or
    "vf2pf")

In particular this patch renames:
  - adf_pf_enable_vf2pf_comms() in adf_enable_pf2vf_comms()
  - enable_vf2pf_comms() in enable_pfvf_comms()
Signed-off-by: NMarco Chiappero <marco.chiappero@intel.com>
Co-developed-by: NGiovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: NGiovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: NFiona Trahe <fiona.trahe@intel.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>