x86 gart: remove unnecessary initialization

There is no point to have such initialization in struct dma_mapping_ops.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/pci-gart_64.c

@@ -715,12 +715,6 @@ extern int agp_amd64_init(void);
 static struct dma_mapping_ops gart_dma_ops = {
 	.map_single			= gart_map_single,
 	.unmap_single			= gart_unmap_single,
-	.sync_single_for_cpu		= NULL,
-	.sync_single_for_device		= NULL,
-	.sync_single_range_for_cpu	= NULL,
-	.sync_single_range_for_device	= NULL,
-	.sync_sg_for_cpu		= NULL,
-	.sync_sg_for_device		= NULL,
 	.map_sg				= gart_map_sg,
 	.unmap_sg			= gart_unmap_sg,
 	.alloc_coherent			= gart_alloc_coherent,