igb: Combine all flag info fields into a single tx_flags structure

This change is meant to combine all of the TX flags fields into one u32
flags field so that it can be stored into the tx_buffer_info structure.
This includes the time stamp flag as well as mapped_as_page flag info.

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>