igbvf: remove Tx hang detection

Removed Tx hang detection mechanism from igbvf.
This mechanism has no affect and can cause false alarm message in some cases.

Signed-off-by: Lior Levy <lior.levy@intel.com>
Tested-by: Jeff Pieper <jeffrey.e.pieper@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>