sh5 never became a product and has probably never really worked.

Remove it by recursively deleting all associated Kconfig options
and all corresponding files.
Reviewed-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NRich Felker <dalias@libc.org>