arch: move CODE_DATA_RELOCATION to top level

Support for CODE_DATA_RELOCATION is not inherently limited to ARM, so
move the Kconfig definition to top-level so it can be used by other
architectures. Since support is opt-in (requiring linker script
support), add a helper symbol enabled by architecture config that gates
whether CODE_DATA_RELOCATION is available instead of listing all
supported systems inline.

Signed-off-by: Peter Marheine <pmarheine@chromium.org>