i40e: fix "dump port" command when NPAR enabled

When using the debugfs to issue the "dump port" command
with NPAR enabled, the firmware reports back with invalid argument.

The issue occurs because the pf->mac_seid was used to perform the query.
This is fine when NPAR is disabled because the switch ID == pf->mac_seid,
however this is not the case when NPAR is enabled.  This fix instead
goes through the VSI to determine the correct ID to use in either case.

Change-ID: I0cd67913a7f2c4a2962e06d39e32e7447cc55b6a
Signed-off-by: Alan Brady <alan.brady@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>