exportfs: Complete kernel-doc for struct export_operations

Write down the missing members definitions for struct export_operations,
using as a reference the commit messages that created the members.

Signed-off-by: André Almeida <andrealmeid@igalia.com>
Link: https://patch.msgid.link/20260112-tonyk-fs_uuid-v1-3-acc1889de772@igalia.com
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: andrealmeid

include/linux/exportfs.h

@@ -201,7 +201,7 @@ struct handle_to_path_ctx {
  * @commit_metadata: commit metadata changes to stable storage
  *
  * See Documentation/filesystems/nfs/exporting.rst for details on how to use
- * this interface correctly.
+ * this interface correctly and the definition of the flags.
  *
  * @encode_fh:
  *    @encode_fh should store in the file handle fragment @fh (using at most
@@ -252,6 +252,19 @@ struct handle_to_path_ctx {
  * @commit_metadata:
  *    @commit_metadata should commit metadata changes to stable storage.
  *
+ * @get_uuid:
+ *    Get a filesystem unique signature exposed to clients.
+ *
+ * @map_blocks:
+ *    Map and, if necessary, allocate blocks for a layout.
+ *
+ * @commit_blocks:
+ *    Commit blocks in a layout once the client is done with them.
+ *
+ * @flags:
+ *    Allows the filesystem to communicate to nfsd that it may want to do things
+ *    differently when dealing with it.
+ *
  * Locking rules:
  *    get_parent is called with child->d_inode->i_rwsem down
  *    get_name is not (which is possibly inconsistent)