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/m68k/kernel/dma.c

@@ -76,8 +76,6 @@ static void *m68k_dma_alloc(struct device *dev, size_t size,
 		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
 {
 	void *ret;
-	/* ignore region specifiers */
-	gfp &= ~(__GFP_DMA | __GFP_HIGHMEM);
 
 	if (dev == NULL || (*dev->dma_mask < 0xffffffff))
 		gfp |= GFP_DMA;