fgraph: Make pid_str size match the comment

The comment above buffer mentions sign, 10 bytes width for number and null
terminator, but buffer itself isn't large enough to hold that much data.

This is a cosmetic change, since PID cannot be negative, other than -1.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Artem Sadovnikov <[email protected]>
Reviewed-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: Artem Sadovnikov

kernel/trace/trace_functions_graph.c

@@ -513,7 +513,7 @@ static void print_graph_proc(struct trace_seq *s, pid_t pid)
 {
 	char comm[TASK_COMM_LEN];
 	/* sign + log10(MAX_INT) + '\0' */
-	char pid_str[11];
+	char pid_str[12];
 	int spaces = 0;
 	int len;
 	int i;