ia64: clean up swiotlb support

Move the few remaining bits of swiotlb glue towards their callers,
and remove the pointless on ia64 swiotlb variable.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian König <christian.koenig@amd.com>

arch/ia64/kernel/dma-mapping.c

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/dma-mapping.h>
+#include <linux/swiotlb.h>
 #include <linux/export.h>
 
 /* Set this to 1 if there is a HW IOMMU in the system */
@@ -23,3 +24,11 @@ const struct dma_map_ops *dma_get_ops(struct device *dev)
 	return dma_ops;
 }
 EXPORT_SYMBOL(dma_get_ops);
+
+#ifdef CONFIG_SWIOTLB
+void __init swiotlb_dma_init(void)
+{
+	dma_ops = &swiotlb_dma_ops;
+	swiotlb_init(1);
+}
+#endif