i40e: fix misleading message about promisc setting on un-trusted VF

A refactor of the i40e_vc_config_promiscuous_mode_msg function moved
the check for un-trusted VF into another function. We have to lie to
an un-trusted VF that its request to set promiscuous mode is
successful even when it is not because we don't want the VF to find
out its trust status this way. With the refactor, we were running into
a case where even though we were not setting promiscuous mode for an
un-trusted VF, we still printed a misleading message that it was
successful.

This patch fixes that by ensuring that a success message is printed
on the host side only when the promiscuous mode change has been
successful.

Signed-off-by: Harshitha Ramamurthy <harshitha.ramamurthy@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>