yaml-to-kml.py: Link to graphs on kernel.org

The key ids currently link to pgp.cs.uu.nl, which has been defunct for a
while.  Link to the graphs in the pgpkeys repo on kernel.org instead to
avoid being dependent on 3rd party services.  Developers looking for
signatures may use the graphs to gauge the position of potential signers
in the kernel web of trust.

This requires that key ids are exactly 16 hex characters long to match
filenames in the pgpkeys repo.  Many entries use only 8 hex characters,
a few use 40.  Expand or shorten the key ids as necessary and remove
whitespace.

The following 15 users are not on the kernel keyring, so clicking their
key id will continue to result in an error message:

  agrimberg.yaml
  crq.yaml
  davem.yaml	(*)
  glommer.yaml
  hauke.yaml
  jaegeuk.yaml
  jeremy.yaml	(*)
  jesper.yaml
  jimix.yaml
  jlbec.yaml
  lizf.yaml
  mcoquelin.yaml
  mdomsch.yaml	(*)
  mmarek.yaml
  sage.yaml	(*)

Users marked (*) reference a key id which I could not find on
keyserver.ubuntu.com.  Those key ids might be outdated.

Signed-off-by: Lukas Wunner <lukas@wunner.de>