[ppc] Fix build breakage for all non-4xx PowerPC variants.

- adapt to the more generic EXCEPTION_PROLOG and CRIT_EXCEPTION macros
- minor 4xx cleanup
diff --git a/include/mpc86xx.h b/include/mpc86xx.h
index 673bfed..9fd349a 100644
--- a/include/mpc86xx.h
+++ b/include/mpc86xx.h
@@ -8,7 +8,7 @@
 #define __MPC86xx_H__
 
 #define EXC_OFF_SYS_RESET	0x0100	/* System reset	offset */
-
+#define _START_OFFSET		EXC_OFF_SYS_RESET
 
 /*
  * platform register addresses