e1000: Do not perform reset in reset_task if we are already down

We are seeing a deadlock in e1000 down when NAPI is being disabled. Looking
over the kernel function trace of the system it appears that the interface
is being closed and then a reset is hitting which deadlocks the interface
as the NAPI interface is already disabled.

To prevent this from happening I am disabling the reset task when
__E1000_DOWN is already set. In addition code has been added so that we set
the __E1000_DOWN while holding the __E1000_RESET flag in e1000_close in
order to guarantee that the reset task will not run after we have started
the close call.

Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
Tested-by: Maxim Zhukov <mussitantesmortem@gmail.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>