drm/sitronix: Remove broken backwards-compatibility layer

When moving the Sitronix DRM drivers and renaming their Kconfig symbols,
the old symbols were kept, aiming to provide a seamless migration path
when running "make olddefconfig" or "make oldconfig".

However, the old compatibility symbols are not visible.  Hence unless
they are selected by another symbol (which they are not), they can never
be enabled, and no backwards compatibility is provided.

Drop the broken mechanism and the old symbols.

Fixes: 9b8f3200 ("drm/sitronix: move tiny Sitronix drivers to their own subdir")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20395b14effe5e2e05a4f0856fdcda51c410329d.1747751592.git.geert+renesas@glider.be


Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>