blackfin: sync data in blackfin write buffer

Sync data in blackfin write buffer to DRAM before return from
copy_to_user.
Otherwise, application may read wrong data from stat syscall occasionally.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bob Liu <lliubbo@gmail.com>
diff --git a/arch/blackfin/include/asm/uaccess.h b/arch/blackfin/include/asm/uaccess.h
index 461bb54..57701c3 100644
--- a/arch/blackfin/include/asm/uaccess.h
+++ b/arch/blackfin/include/asm/uaccess.h
@@ -191,6 +191,7 @@
 		memcpy((void __force *)to, from, n);
 	else
 		return n;
+	SSYNC();
 	return 0;
 }