xattr: fix kernel-doc for mnt_userns and vfs xattr helpers

Fix kernel-doc warnings in xattr.c:

../fs/xattr.c:257: warning: Function parameter or member 'mnt_userns' not described in '__vfs_setxattr_locked'
../fs/xattr.c:485: warning: Function parameter or member 'mnt_userns' not described in '__vfs_removexattr_locked'

and fix one function whose kernel-doc was not in the correct format.

Link: https://lore.kernel.org/r/20210216042929.8931-4-rdunlap@infradead.org
Fixes: 71bc356 ("commoncap: handle idmapped mounts")
Fixes: b1ab7e4 ("VFS: Factor out part of vfs_setxattr so it can be called from the SELinux hook for inode_setsecctx.")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: David P. Quigley <dpquigl@tycho.nsa.gov>
Cc: James Morris <jmorris@namei.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Author: rddunlap

fs/xattr.c

@@ -186,12 +186,12 @@ EXPORT_SYMBOL(__vfs_setxattr);
  *  __vfs_setxattr_noperm - perform setxattr operation without performing
  *  permission checks.
  *
- *  @mnt_userns - user namespace of the mount the inode was found from
- *  @dentry - object to perform setxattr on
- *  @name - xattr name to set
- *  @value - value to set @name to
- *  @size - size of @value
- *  @flags - flags to pass into filesystem operations
+ *  @mnt_userns: user namespace of the mount the inode was found from
+ *  @dentry: object to perform setxattr on
+ *  @name: xattr name to set
+ *  @value: value to set @name to
+ *  @size: size of @value
+ *  @flags: flags to pass into filesystem operations
  *
  *  returns the result of the internal setxattr or setsecurity operations.
  *
@@ -242,6 +242,7 @@ int __vfs_setxattr_noperm(struct user_namespace *mnt_userns,
  * __vfs_setxattr_locked - set an extended attribute while holding the inode
  * lock
  *
+ *  @mnt_userns: user namespace of the mount of the target inode
  *  @dentry: object to perform setxattr on
  *  @name: xattr name to set
  *  @value: value to set @name to
@@ -473,6 +474,7 @@ EXPORT_SYMBOL(__vfs_removexattr);
  * __vfs_removexattr_locked - set an extended attribute while holding the inode
  * lock
  *
+ *  @mnt_userns: user namespace of the mount of the target inode
  *  @dentry: object to perform setxattr on
  *  @name: name of xattr to remove
  *  @delegated_inode: on return, will contain an inode pointer that