fbdev: sbuslib: remove unused FBIOSCURSOR32 helper

No driver implements FBIOSCURSOR, so this function has no purpose
and can be removed. Apparently it was added in linux-2.1.44 to handle
compatibility for drivers/sbus/char/sunfb.c but lost its purpose when
that driver got rewritten in linux-2.5.63.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200918100926.1447563-2-arnd@arndb.de