igb: use ARRAY_SIZE to replace calculating sizeof(a)/sizeof(a[0])

igb: use ARRAY_SIZE to replace calculating sizeof(a)/sizeof(a[0])

Orabug: 21792102

Use the ARRAY_SIZE macro rather than calculating sizeof(a)/sizeof(a[0]).
Also directly replace the code rather than using an unnecessary define.

Reported-by: Maninder Singh <maninder1.s@samsung.com>
Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Todd Fujinaka <todd.fujinaka@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
(cherry picked from commit 9fa0452b645efdff439948a5cf448b8e497340e9)
Signed-off-by: Brian Maly <brian.maly@oracle.com>