tracing: probeevent: Do not accumulate on ret variable

Do not accumulate strlen result on "ret" local variable, because
it is accumulated on "total" local variable for array case.

Link: http://lkml.kernel.org/r/155723735237.9149.3192150444705457531.stgit@devnote2

Fixes: 40b53b77 ("tracing: probeevent: Add array type support")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/trace_probe_tmpl.h

@@ -88,7 +88,7 @@ process_fetch_insn_bottom(struct fetch_insn *code, unsigned long val,
 	/* 3rd stage: store value to buffer */
 	if (unlikely(!dest)) {
 		if (code->op == FETCH_OP_ST_STRING) {
-			ret += fetch_store_strlen(val + code->offset);
+			ret = fetch_store_strlen(val + code->offset);
 			code++;
 			goto array;
 		} else