ftrace: Always inline ftrace_hash_empty() helper function

The ftrace_hash_empty() function is a simple test:

	return !hash || !hash->count;

But gcc seems to want to make it a call. As this is in an extreme
hot path of the function tracer, there's no reason it needs to be
a call. I only wrote it to be a helper function anyway, otherwise
it would have been inlined manually.

Force gcc to inline it, as it could have also been a macro.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 61f39f8..98fa931 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1105,7 +1105,7 @@
 static struct ftrace_page	*ftrace_pages_start;
 static struct ftrace_page	*ftrace_pages;
 
-static bool ftrace_hash_empty(struct ftrace_hash *hash)
+static bool __always_inline ftrace_hash_empty(struct ftrace_hash *hash)
 {
 	return !hash || !hash->count;
 }