e1000e: add rtnl_lock() to e1000_reset_task

e1000e: add rtnl_lock() to e1000_reset_task

A possible race condition was found in e1000_reset_task,
after discovering a similar issue in igb driver via
commit dfc571cf22be ("igb: reinit_locked() should be called
with rtnl_lock").

Added rtnl_lock() and rtnl_unlock() to avoid this.

Fixes: 3f32e81cc0ea ("[E1000E]: New pci-express e1000 driver (currently for ICH9 devices only)")
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Vitaly Lifshits <vitaly.lifshits@intel.com>
Tested-by: Dvora Fuxbrumer <dvorax.fuxbrumer@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>