match: Use the SINK_INPUT_FIXATE hook instead of NEW.
The callback relies on the sample spec being finalized, which is not
true with the NEW hook.
In case you're wondering about the "hook EARLY - 1, to match before
stream-restore" comment that was not changed even though the code that
the comment concerned was changed: the comment was apparently written
at a time when module-stream-restore used the NEW hook too, and later
stream-restore has been changed to use the FIXATE hook. So, the
comment was wrong/nonsensical before this patch. Since these two
modules now use the same hook again, the comment makes sense again.
BugLink: https://bugs.freedesktop.org/show_bug.cgi?id=55135