igb: remove unnecessary adapter->hw calls when just hw-> will do.

There were several spots in the code making calls to adapter->hw when they
could have just been accessing hw-> directly.  I cleaned up the spots where
this was visibly apparent.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>