nvme: fix NULL derefence in nvme_ctrl_fast_io_fail_tmo_show/store

mainline inclusion
from mainline-v5.13-rc1
commit d6609084
category: bugfix
bugzilla: NA
CVE: NA
Link: https://gitee.com/openeuler/kernel/issues/I4JFPM?from=project-issue

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

Adding entry for dev_attr_fast_io_fail_tmo to avoid the kernel crash
while reading and writing the fast_io_fail_tmo.

Fixes: 09fbed63 (nvme: export fast_io_fail_tmo to sysfs)
Signed-off-by: NGopal Tiwari <gtiwari@redhat.com>
Reviewed-by: NKeith Busch <kbusch@kernel.org>
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: Njiangtao <jiangtao62@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/nvme/host/core.c

@@ -3157,6 +3157,8 @@ static umode_t nvme_dev_attrs_are_visible(struct kobject *kobj,
 		return 0;
 	if (a == &dev_attr_address.attr && !ctrl->ops->get_address)
 		return 0;
+	if (a == &dev_attr_fast_io_fail_tmo.attr && !ctrl->opts)
+		return 0;
 
 	return a->mode;
 }