Boot: Harden critical path against fault attacks

Add fault attack mitigation measures to code which is vital for
the correct validation of images.

Change-Id: Iea12a6eac9c3f516ed8c96a6df44b7a4086dd7f5
Signed-off-by: Raef Coles <raef.coles@arm.com>
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
7 files changed