Documentation: ioctl: add entry for nsfs.h

All userspace ioctls major/magic number should be documented in
Documentation/userspace-api/ioctl/ioctl-number.rst, so add
the entry for <linux/nsfs.h>.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: Serge Hallyn <serge@hallyn.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: linux-doc@vger.kernel.org
Cc: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20210210182248.18101-1-rdunlap@infradead.orgSigned-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/userspace-api/ioctl/ioctl-number.rst

@@ -347,6 +347,7 @@ Code  Seq#    Include File                                           Comments
 0xB5  00-0F  uapi/linux/rpmsg.h                                      <mailto:linux-remoteproc@vger.kernel.org>
 0xB6  all    linux/fpga-dfl.h
 0xB7  all    uapi/linux/remoteproc_cdev.h                            <mailto:linux-remoteproc@vger.kernel.org>
+0xB7  all    uapi/linux/nsfs.h                                       <mailto:Andrei Vagin <avagin@openvz.org>>
 0xC0  00-0F  linux/usb/iowarrior.h
 0xCA  00-0F  uapi/misc/cxl.h
 0xCA  10-2F  uapi/misc/ocxl.h