Bug Fix arch/ia64/kernel/pci-dma.c: fix recursive dma_supported() call in iommu_dma_supported()

In commit 160c1d8e,
dma_ops->dma_supported = iommu_dma_supported;

This dma_ops->dma_supported is first called in platform_dma_init() during kernel
boot. Then dma_ops->dma_supported will be called recursively in
iommu_dma_supported.

Kernel can not boot because kernel can not get out of iommu_dma_supported until
it runs out of stack memory.
Signed-off-by: NFenghua Yu <fenghua.yu@intel.com>

arch/ia64/kernel/pci-dma.c

@@ -69,11 +69,6 @@ iommu_dma_init(void)
 
 int iommu_dma_supported(struct device *dev, u64 mask)
 {
-	struct dma_map_ops *ops = platform_dma_get_ops(dev);
-
-	if (ops->dma_supported)
-		return ops->dma_supported(dev, mask);
-
 	/* Copied from i386. Doesn't make much sense, because it will
 	   only work for pci_alloc_coherent.
 	   The caller just has to use GFP_DMA in this case. */