ARM: Drop CMDLINE_FORCE dependency on !ARCH_MULTIPLATFORM

On older platforms that boot an image with an appended DTB, or where
the boot loader has no support for updating chosen/bootargs, it is
common to rely on CMDLINE_FORCE.

While a fixed command line can make the kernel unbootable on other
platforms, it is not guaranteed to cause that.  E.g. all Renesas boards
use the same chosen/bootargs in upstream DTS, which works fine if your
DHCP server hands out proper nfsroot parameters.

Fixes: 84fc8636 ("ARM: make ARCH_MULTIPLATFORM user-visible")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>