i40e: Fix I40E_FLAG_VF_VLAN_PRUNING value

Commit c87c938f ("i40e: Add VF VLAN pruning") added new
PF flag I40E_FLAG_VF_VLAN_PRUNING but its value collides with
existing I40E_FLAG_TOTAL_PORT_SHUTDOWN_ENABLED flag.

Move the affected flag at the end of the flags and fix its value.

Reproducer:
[root@cnb-03 ~]# ethtool --set-priv-flags enp2s0f0np0 link-down-on-close on
[root@cnb-03 ~]# ethtool --set-priv-flags enp2s0f0np0 vf-vlan-pruning on
[root@cnb-03 ~]# ethtool --set-priv-flags enp2s0f0np0 link-down-on-close off
[ 6323.142585] i40e 0000:02:00.0: Setting link-down-on-close not supported on this port (because total-port-shutdown is enabled)
netlink error: Operation not supported
[root@cnb-03 ~]# ethtool --set-priv-flags enp2s0f0np0 vf-vlan-pruning off
[root@cnb-03 ~]# ethtool --set-priv-flags enp2s0f0np0 link-down-on-close off

The link-down-on-close flag cannot be modified after setting vf-vlan-pruning
because vf-vlan-pruning shares the same bit with total-port-shutdown flag
that prevents any modification of link-down-on-close flag.

Fixes: c87c938f

 ("i40e: Add VF VLAN pruning")
Cc: Mateusz Palczewski <mateusz.palczewski@intel.com>
Cc: Simon Horman <horms@kernel.org>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Pucha Himasekhar Reddy <himasekharx.reddy.pucha@intel.com> (A Contingent worker at Intel)
Signed-off-by: David S. Miller <davem@davemloft.net>