h8300: remove stale bindings and symlink

These four files are left over from the h8300 removal.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>