MAINTAINERS: mark ax25 as Orphan

MAINTAINERS: mark ax25 as Orphan

We haven't heard from Ralf for two years, according to lore.
We get a constant stream of "fixes" to ax25 from people using
code analysis tools. Nobody is reviewing those, let's reflect
this reality in MAINTAINERS.

Subsystem AX.25 NETWORK LAYER
  Changes 9 / 59 (15%)
  (No activity)
  Top reviewers:
    [2]: mkl@pengutronix.de
    [2]: edumazet@google.com
    [2]: stefan@datenfreihafen.org
  INACTIVE MAINTAINER Ralf Baechle <ralf@linux-mips.org>

Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240109164517.3063131-7-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>