media: s5p_cec: decrement usage count if disabled

There's a bug at s5p_cec_adap_enable(): if called to
disable the device, it should call pm_runtime_put()
instead of pm_runtime_disable(), as the goal here is to
decrement the usage_count and not to disable PM runtime.

Reported-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Fixes: 1bcbf6f4 ("[media] cec: s5p-cec: Add s5p-cec driver")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>