powerpc: Rename exception.h to exception-64s.h

The file include/asm/exception.h contains definitions
that are specific to exception handling on 64-bit server
type processors.

This renames the file to exception-64s.h to reflect that
fact and avoid confusion.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
index eb89811..72644cf 100644
--- a/arch/powerpc/kernel/exceptions-64s.S
+++ b/arch/powerpc/kernel/exceptions-64s.S
@@ -12,6 +12,8 @@
  *
  */
 
+#include <asm/exception-64s.h>
+
 /*
  * We layout physical memory as follows:
  * 0x0000 - 0x00ff : Secondary processor spin code