of/selftest: Fix GPIOs selftest to cover the 7th case

The of_gpio_named_count() self test doesn't hit the out-of-range
condition even though it is coded. Fix the bug by increasing the for
loop range by one.
Reported-by: NAndreas Larsson <andreas@gaisler.com>
Cc: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/of/selftest.c

@@ -35,7 +35,7 @@ static void __init of_selftest_parse_phandle_with_args(void)
 		return;
 	}
 
-	for (i = 0; i < 7; i++) {
+	for (i = 0; i < 8; i++) {
 		bool passed = true;
 		rc = of_parse_phandle_with_args(np, "phandle-list",
 						"#phandle-cells", i, &args);