ixgbe: use BIT() macro

Several areas of ixgbe were written before widespread usage of the
BIT(n) macro. With the impending release of GCC 6 and its associated new
warnings, some usages such as (1 << 31) have been noted within the ixgbe
driver source. Fix these wholesale and prevent future issues by simply
using BIT macro instead of hand coded bit shifts.

Also fix a few shifts that are shifting values into place by using the
'u' prefix to indicate unsigned. It doesn't strictly matter in these
cases because we're not shifting by too large a value, but these are all
unsigned values and should be indicated as such.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>