dma-mapping: clear harmful GFP_* flags in common code

Lift the code from x86 so that we behave consistently.  In the future we
should probably warn if any of these is set.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org> [m68k]

arch/h8300/kernel/dma.c

@@ -16,9 +16,6 @@ static void *dma_alloc(struct device *dev, size_t size,
 {
 	void *ret;
 
-	/* ignore region specifiers */
-	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM);
-
 	if (dev == NULL || (*dev->dma_mask < 0xffffffff))
 		gfp |= GFP_DMA;
 	ret = (void *)__get_free_pages(gfp, get_order(size));