m68k: mcf: Remove overloading version_string

There is no need to overload version_string at the end of start.S files.
Common implementation of version_string should be fine.

Signed-off-by: Pali Rohár <pali@kernel.org>
[trini: Keep the align, it's important for the rest of linkage]
Signed-off-by: Tom Rini <trini@konsulko.com>