ASoC: simple-card: fixup refcount_t underflow

commit da215354

 ("ASoC: simple-card: merge simple-scu-card")
merged simple-card and simple-scu-card. Then it had refcount
underflow bug. This patch fixup it.
We will get below error without this patch.

	OF: ERROR: Bad of_node_put() on /sound
	CPU: 3 PID: 237 Comm: kworker/3:1 Not tainted 5.0.0-rc6+ #1514
	Hardware name: Renesas H3ULCB Kingfisher board based on r8a7795 ES2.0+ (DT)
	Workqueue: events deferred_probe_work_func
	Call trace:
	 dump_backtrace+0x0/0x150
	 show_stack+0x24/0x30
	 dump_stack+0xb0/0xec
	 of_node_release+0xd0/0xd8
	 kobject_put+0x74/0xe8
	 of_node_put+0x24/0x30
	 __of_get_next_child+0x50/0x70
	 of_get_next_child+0x40/0x68
	 asoc_simple_card_probe+0x604/0x730
	 platform_drv_probe+0x58/0xa8
	 ...
Reported-by: Vicente Bergas <vicencb@gmail.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>

Signed-off-by: Mark Brown <broonie@kernel.org>