function_graph: Make fgraph_do_direct static key static

The static branch key "fgraph_do_direct" was not declared static but is
only used in one file. Change it to a static variable.

Link: https://lore.kernel.org/linux-trace-kernel/[email protected]

Cc: Mark Rutland <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Andrew Morton <[email protected]>
Fixes: cc60ee8 ("function_graph: Use static_call and branch to optimize entry function")
Reported-by: kernel test robot <[email protected]>
Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

kernel/trace/fgraph.c

@@ -515,7 +515,7 @@ static struct fgraph_ops fgraph_stub = {
 static struct fgraph_ops *fgraph_direct_gops = &fgraph_stub;
 DEFINE_STATIC_CALL(fgraph_func, ftrace_graph_entry_stub);
 DEFINE_STATIC_CALL(fgraph_retfunc, ftrace_graph_ret_stub);
-DEFINE_STATIC_KEY_TRUE(fgraph_do_direct);
+static DEFINE_STATIC_KEY_TRUE(fgraph_do_direct);
 
 /**
  * ftrace_graph_stop - set to permanently disable function graph tracing