uapi, fsopen: use square brackets around "fscontext" [ver #2]

Make the name of the anon inode fd "[fscontext]" instead of "fscontext".
This is minor but most core-kernel anon inode fds already carry square
brackets around their name:

[eventfd]
[eventpoll]
[fanotify]
[io_uring]
[pidfd]
[signalfd]
[timerfd]
[userfaultfd]

For the sake of consistency lets do the same for the fscontext anon inode
fd that comes with the new mount api.

Signed-off-by: Christian Brauner <christian@brauner.io>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/fsopen.c

@@ -92,7 +92,7 @@ static int fscontext_create_fd(struct fs_context *fc, unsigned int o_flags)
 {
  int fd;
 
- fd = anon_inode_getfd("fscontext", &fscontext_fops, fc,
+ fd = anon_inode_getfd("[fscontext]", &fscontext_fops, fc,
  O_RDWR | o_flags);
  if (fd < 0)
  put_fs_context(fc);