netfs: Update main API document

Bring the netfs documentation up to date.

Signed-off-by: David Howells <[email protected]>
Link: https://lore.kernel.org/[email protected]
Reviewed-by: "Paulo Alcantara (Red Hat)" <[email protected]>
cc: Jeff Layton <[email protected]>
cc: Viacheslav Dubeyko <[email protected]>
cc: Alex Markuze <[email protected]>
cc: Timothy Day <[email protected]>
cc: Jonathan Corbet <[email protected]>
cc: [email protected]
cc: [email protected]
cc: [email protected]
Signed-off-by: Christian Brauner <[email protected]>

Author: dhowells