x86: Add flush_write_buffers in nommu functions

This patch adds flush_write_buffers() in some functions of pci-nommu_64.c
They are added anywhere i386 would also have it. This is not a problem
for x86_64, since flush_rite_buffers() an nop for it.
Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/pci-nommu_64.c

@@ -32,6 +32,7 @@ nommu_map_single(struct device *hwdev, phys_addr_t paddr, size_t size,
 	dma_addr_t bus = paddr;
 	if (!check_addr("map_single", hwdev, bus, size))
 				return bad_dma_address;
+	flush_write_buffers();
 	return bus;
 }
 
@@ -64,6 +65,7 @@ static int nommu_map_sg(struct device *hwdev, struct scatterlist *sg,
 			return 0;
 		s->dma_length = s->length;
 	}
+	flush_write_buffers();
 	return nents;
 }