leds: gpio: Fix device teardown on probe deferral

In gpio_leds_create(), when devm_get_gpiod_from_child() fails with
-EPROBE_DEFER on the second gpio led to be created, the first already
registered led is not torn down properly. This causes create_gpio_led()
to fail for the first led on re-probe().

Fix this misbehaviour by incrementing num_leds only if all
potentially failing calls completed successfully.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Acked-by: Jacek Anaszewski <j.anaszewski@samsung.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>