Add and use the new helper function adf_get_pmisc_base() where convenient.

Also:
- remove no longer shared variables
- leverage other utilities, such as GET_PFVF_OPS(), as a consequence
- consistently use the "pmisc_addr" name for the returned value of this
  new helper
Signed-off-by: Marco Chiappero <marco.chiappero@intel.com>
Co-developed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Reviewed-by: Fiona Trahe <fiona.trahe@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>