[ARM] Export dma_sync_sg_for_device()

Noticed by Martin Michlmayr, this missing export prevents IEEE1394
from building with:

ERROR: "dma_sync_sg_for_device" [drivers/ieee1394/ieee1394.ko] undefined!
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/common/dmabounce.c

@@ -650,7 +650,8 @@ EXPORT_SYMBOL(dma_map_sg);
 EXPORT_SYMBOL(dma_unmap_sg);
 EXPORT_SYMBOL(dma_sync_single_for_cpu);
 EXPORT_SYMBOL(dma_sync_single_for_device);
-EXPORT_SYMBOL(dma_sync_sg);
+EXPORT_SYMBOL(dma_sync_sg_for_cpu);
+EXPORT_SYMBOL(dma_sync_sg_for_device);
 EXPORT_SYMBOL(dmabounce_register_dev);
 EXPORT_SYMBOL(dmabounce_unregister_dev);