[PATCH net-next] Documentation/networking: update l2tp docs

From: James Chapman Kernel documentation of L2TP has not been kept up to date and lacks coverage of some L2TP APIs. While addressing this, refactor to improve readability, separating the parts which focus on user APIs and internal implementation into sections. Signed-off-by: James Chapman ---

[PATCH net-next v2] Documentation/networking: update l2tp docs

From: James Chapman Kernel documentation of L2TP has not been kept up to date and lacks coverage of some L2TP APIs. While addressing this, refactor to improve readability, separating the parts which focus on user APIs and internal implementation into sections. Changes in v2: - fix checkpatch w