drm/nouveau/debugfs: fix file release memory leak

stable inclusion
from stable-v4.19.211
commit 1508b09945bde393326a9dab73b1fc35f672d771
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4NL
CVE: CVE-2021-47423

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1508b09945bde393326a9dab73b1fc35f672d771



--------------------------------

[ Upstream commit f5a8703a ]

When using single_open() for opening, single_release() should be
called, otherwise the 'op' allocated in single_open() will be leaked.

Fixes: 6e9fc177 ("drm/nouveau/debugfs: add copy of sysfs pstate interface ported to debugfs")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210911075023.3969054-2-yangyingliang@huawei.com


Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Zheng Zucheng <zhengzucheng@huawei.com>