dma-mapping: allow using the global coherent pool for !ARM

Switch an ifdef so that the global coherent pool is initialized for
any architecture that selects the DMA_GLOBAL_POOL symbol insted of
hardcoding ARM.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Dillon Min <dillon.minfei@gmail.com>

kernel/dma/coherent.c

@@ -361,7 +361,9 @@ static int __init rmem_dma_setup(struct reserved_mem *rmem)
 		pr_err("Reserved memory: regions without no-map are not yet supported\n");
 		return -EINVAL;
 	}
+#endif
 
+#ifdef CONFIG_DMA_GLOBAL_POOL
 	if (of_get_flat_dt_prop(node, "linux,dma-default", NULL)) {
 		WARN(dma_reserved_default_memory,
 		     "Reserved memory: region for default DMA coherent area is redefined\n");