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Since Trusted OS firmware may have extra images, need to
assign new uuid and image id for them.
The TBBR chain of trust has been extended to add support
for the new images within the existing Trusted OS firmware
content certificate.

Change-Id: I678dac7ba1137e85c5779b05e0c4331134c10e06
Signed-off-by: Summer Qin <summer.qin@arm.com>