lib/dma-noop: Only build dma_noop_ops for s390 and m32r

Reduce the kernel size by only building dma_noop_ops for those
architectures that actually use it. This was suggested by
Christoph Hellwig.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Doug Ledford <dledford@redhat.com>