The superhyway bus driver was only referenced on SH4-202, which is now gone,
so remove it all as well.

I could find no trace of anything ever calling superhyway_register_driver(),
not in the git history but also not on the web, so I assume this has never
served any purpose on mainline kernels.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>
Link: https://lore.kernel.org/r/20230914155523.3839811-3-arnd@kernel.orgSigned-off-by: John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>