e1000e: keep VLAN interfaces functional after rxvlan off

I've got a bug report about an e1000e interface, where a VLAN interface is
set up on top of it:

$ ip link add link ens1f0 name ens1f0.99 type vlan id 99
$ ip link set ens1f0 up
$ ip link set ens1f0.99 up
$ ip addr add 192.168.99.92 dev ens1f0.99

At this point, I can ping another host on vlan 99, ip 192.168.99.91.
However, if I do the following:

$ ethtool -K ens1f0 rxvlan off

Then no traffic passes on ens1f0.99. It comes back if I toggle rxvlan on
again. I'm not sure if this is actually intended behavior, or if there's a
lack of software VLAN stripping fallback, or what, but things continue to
work if I simply don't call e1000e_vlan_strip_disable() if there are
active VLANs (plagiarizing a function from the e1000 driver here) on the
interface.

Also slipped a related-ish fix to the kerneldoc text for
e1000e_vlan_strip_disable here...

Signed-off-by: Jarod Wilson <jarod@redhat.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>