i40e: Decrease the scope of rtnl lock

Previously rtnl lock was held during whole reset procedure that
was stopping other PFs running their reset procedures. In the result
reset was not handled properly and host reset was the only way
to recover.

Change-ID: I23c0771c0303caaa7bd64badbf0c667e25142954
Signed-off-by: Maciej Sosin <maciej.sosin@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>