igb: Fix removal of unicast MAC filters of VFs

[ Upstream commit 584af821 ]

Move checking condition of VF MAC filter before clearing
or adding MAC filter to VF to prevent potential blackout caused
by removal of necessary and working VF's MAC filter.

Fixes: 1b8b062a ("igb: add VF trust infrastructure")
Signed-off-by: Karen Sornek <karen.sornek@intel.com>
Tested-by: Konrad Jankowski <konrad0.jankowski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>