arm-nommu: don't define arch_teardown_dma_ops

We can just use the default implementation.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NRobin Murphy <robin.murphy@arm.com>

arch/arm/include/asm/dma-mapping.h

@@ -100,8 +100,10 @@ static inline unsigned long dma_max_pfn(struct device *dev)
 extern void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 			       const struct iommu_ops *iommu, bool coherent);
 
+#ifdef CONFIG_MMU
 #define arch_teardown_dma_ops arch_teardown_dma_ops
 extern void arch_teardown_dma_ops(struct device *dev);
+#endif
 
 /* do not use this function in a driver */
 static inline bool is_device_dma_coherent(struct device *dev)

arch/arm/mm/dma-mapping-nommu.c

@@ -237,7 +237,3 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 
 	set_dma_ops(dev, dma_ops);
 }
-
-void arch_teardown_dma_ops(struct device *dev)
-{
-}