Optionally add new security counter TLV to the protected image manifest
and also introduce a new command line option for the imgtool to specify
the value of this counter. The security counter can be used in rollback
protection to compare the new image's security counter against the
active counter value. Its value can be independent from the image
version, but if the 'auto' keyword is passed in the argument list of the
script then it will be generated from the version number (not including
the build number).
The value of the security counter is security critical data. Therefore,
it must be part of the protected TLV area.
Change-Id: I45926d22364d0528164f50fa379abf050bdf65ff
Signed-off-by: David Vincze <david.vincze@arm.com>