vfio/amba: Mark for removal

vfio/amba: Mark for removal

vfio-amba has only been touched to keep up with the rest of the code
base for the past 10 years.  We have no basis to believe that it's
currently tested or used.  Mark it for deprecation.

Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Mostafa Saleh <smostafa@google.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Link: https://lore.kernel.org/r/20250825175807.3264083-2-alex.williamson@redhat.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>