media: stm32-dcmi: Fix a reference count leak

Calling pm_runtime_get_sync increments the counter even in case of
failure, causing incorrect ref count if pm_runtime_put is not
called in error handling paths. Thus replace the jump target
"err_release_buffers" by "err_pm_putw".

Fixes: 152e0bf6 ("media: stm32-dcmi: add power saving support")
Signed-off-by: Qiushi Wu <wu000273@umn.edu>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>