igb: Simplify how we populate the RSS key

Instead of storing the RSS key as a character array we can simplify the
configuration by making it a u32 array.  This allows us to just write one
value per register without any unnecessary operations to construct the
value.

This change will produce the same exact key, the only difference is that I
translated the u8 array to a u32 array which will be correctly ordered on
writes to hardware by the cpu_to_le32 operations that are built into the
writel calls.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>