ARM: S5PV210: Remove limiting choice of machine to build

The arch/arm/mach-s5pv210/Kconfig had a choice entry
to choose which of the two machines to build, which is
silly since you can easily build more than one machine
at a time.

Remove the choice entry so that both machines and any
future additions can all build in harmony.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>