docs: Update VME documentation to include kerneldoc comments

Update VME documentation given that kerneldoc comments are now provided.
Add "VME API" section to VME RST to pull in kerneldoc comments.

Signed-off-by: Martyn Welch <martyn.welch@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>