ixgbevf: set the disable state when ixgbevf_qv_disable is called

The ixgbevf_qv_disable function used by CONFIG_NET_RX_BUSY_POLL is broken,
because it does not properly set the IXGBEVF_QV_STATE_DISABLED bit, indicating
that the q_vector should be disabled (and preventing future locks from
obtaining the vector). This patch corrects the issue by setting the disable
state.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>