WAN: split hd6457x.c into hd64570.c and hd64572.c

Supporting both original SCA and SCA-II in one file was nice at some
point but now it's increasingly painful.

Signed-off-by: Krzysztof Hałasa <khc@pm.waw.pl>
diff --git a/drivers/net/wan/n2.c b/drivers/net/wan/n2.c
index 0a566b0..5b9cd2d 100644
--- a/drivers/net/wan/n2.c
+++ b/drivers/net/wan/n2.c
@@ -160,7 +160,7 @@
 
 
 
-#include "hd6457x.c"
+#include "hd64570.c"