perf dwarf-aux: Fix off-by-one in die_get_varname()

The die_get_varname() returns "(unknown_type)" string if it failed to
find a type for the variable.  But it had a space before the opening
parenthesis and it made the closing parenthesis cut off due to the
off-by-one in the string length (14).
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Fixes: 88fd633c ("perf probe: No need to use formatting strbuf method")
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20230612234102.3909116-1-namhyung@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/dwarf-aux.c

@@ -1103,7 +1103,7 @@ int die_get_varname(Dwarf_Die *vr_die, struct strbuf *buf)
 	ret = die_get_typename(vr_die, buf);
 	if (ret < 0) {
 		pr_debug("Failed to get type, make it unknown.\n");
-		ret = strbuf_add(buf, " (unknown_type)", 14);
+		ret = strbuf_add(buf, "(unknown_type)", 14);
 	}
 
 	return ret < 0 ? ret : strbuf_addf(buf, "\t%s", dwarf_diename(vr_die));