[AVR32] Drop GFP_COMP for DMA memory allocations

dma_alloc_coherent wants to split pages after allocation in order to
reduce the memory footprint. This does not work well with GFP_COMP
pages, so drop this flag before allocation.

This patch was forward-ported from BSP 2.0
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>

arch/avr32/mm/dma-coherent.c

@@ -41,6 +41,13 @@ static struct page *__dma_alloc(struct device *dev, size_t size,
 	struct page *page, *free, *end;
 	int order;
 
+	/* Following is a work-around (a.k.a. hack) to prevent pages
+	 * with __GFP_COMP being passed to split_page() which cannot
+	 * handle them.  The real problem is that this flag probably
+	 * should be 0 on AVR32 as it is not supported on this
+	 * platform--see CONFIG_HUGETLB_PAGE. */
+	gfp &= ~(__GFP_COMP);
+
 	size = PAGE_ALIGN(size);
 	order = get_order(size);