x86: avoid unnecessary low zone allocation in Calgary's alloc_coherent

x86's common alloc_coherent (dma_alloc_coherent in dma-mapping.h) sets
up the gfp flag according to the device dma_mask but Calgary doesn't
need it because of virtual mappings. This patch avoids unnecessary low
zone allocation.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Acked-by: Muli Ben-Yehuda <muli@il.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/pci-calgary_64.c

@@ -491,6 +491,8 @@ static void* calgary_alloc_coherent(struct device *dev, size_t size,
 	npages = size >> PAGE_SHIFT;
 	order = get_order(size);
 
+	flag &= ~(__GFP_DMA | __GFP_HIGHMEM | __GFP_DMA32);
+
 	/* alloc enough pages (and possibly more) */
 	ret = (void *)__get_free_pages(flag, order);
 	if (!ret)