Firmware Update (FWU) introduces a new set of images called
SCP_BL2U, BL2U and NS_BL2U, which can be packed in a FWU FIP file.

This patch introduces new UUIDs for the Firmware Update images
and extends the 'fip'create' tool so that these new images can be
packed in a FIP file.

Change-Id: I7c60211b4f3cc265411efb131e6d3c624768f522