[PATCH] riscv: make ZONE_DMA32 optional

[Vladimir Kondratiev]

>I'm wondering how distro kernels will deal with that since some
>platforms will need the ZONE_DMA32 and some others will break when
>enabled as you have shown.

I agree platforms with no ZONE_DMA32 is non-portable,
to address this I will add dependency on NONPORTABLE and re-submit
shortly. Thanks for pointing that.

>Is there a way to make it optional at runtime instead?
Unfortunately no, or at least I see no way to do so

Thanks, Vladimir