ixgbe: Revise populating few registers and macro definitions

Revise populating few registers in ixgbe_get_regs() and macro
definitions.
Before applying patch:
$ du -k objs/drivers/net/ethernet/intel/ixgbe/ixgbe.ko
8572    objs/drivers/net/ethernet/intel/ixgbe/ixgbe.ko
After applying patch:
$ du -k objs/drivers/net/ethernet/intel/ixgbe/ixgbe.ko
8568    objs/drivers/net/ethernet/intel/ixgbe/ixgbe.ko

Signed-off-by: Preethi Banala <preethi.banala@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>