Mk/bsd.options.mk: add OPTIONS_RADIO_${NAME}_${ARCH} support

This is similar to OPTIONS_DEFINE_${ARCH}, allowing radios to
be dependent on ${ARCH} too, useful for ports that requires
the user to choose exactly one execution backend or firmware
payload, where the available choices depend on the architecture
(for example, choosing between specific JIT backends on amd64
versus a different set of backends on aarch64), etc.

PR: ports/294399
Approved by: portmgr (mat)