ixgbevf: fix possible race in the reset subtask

Extend the RTNL lock in ixgbevf_reset_subtask() to protect the state bits
check in addition to the call to ixgbevf_reinit_locked().

This is to make sure that we get the most up-to-date values for the bits
and avoid a possible race when going down.

Suggested-by: Zhiping du <zhipingdu@tencent.com>
Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>