sstatesig: Updates to match bitbake siggen changes
Update the metadata to correspond to the bitbake siggen task specification
format change. This standardises on "<fn>:<task>" everywhere rather than
the "." delimiter that was being used in some places.
This is an API breaking change but means we now have a consistent format
being used throughout the codebase without compatibility APIs.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
