graph-lock: Add GRAPH_UNLOCKED(_PTR)

graph-lock: Add GRAPH_UNLOCKED(_PTR)

For some functions, it is part of their interface to be called without
holding the graph lock. Add a new macro to document this.

The macro expands to TSA_EXCLUDES(), which is a relatively weak check
because it passes in cases where the compiler just doesn't know if the
lock is held. Function pointers can't be checked at all. Therefore, its
primary purpose is documentation.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20230504115750.54437-7-kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>