igbvf: use BIT() macro instead of shifts

To prevent signed bitshift issues, and improve code readability, use the
BIT() macro. Also make use of GENMASK or the unsigned postfix where this
is more appropriate than BIT()

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