arch: Add ARCH_SUPPORTS_ROM_START kconfig symbol

Add an ARCH_SUPPORTS_ROM_START kconfig symbol to mark architectures
that support ROM_START as an argument to zephyr_linker_sources.
This was added so that features relying on this feature could
depend on this kconfig symbol.

Signed-off-by: Yonatan Schachter <yonatan.schachter@gmail.com>