[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/ppc_asm.tmpl b/include/ppc_asm.tmpl
index ad027d6..9f4029f 100644
--- a/include/ppc_asm.tmpl
+++ b/include/ppc_asm.tmpl
@@ -274,7 +274,7 @@
 #define CRIT_EXCEPTION(n, label, hdlr)				\
 	. = n;							\
 label:								\
-	EXCEPTION_PROLOG(csrr0, csrr1);				\
+	EXCEPTION_PROLOG(CSRR0, CSRR1);				\
 	lwz	r3,GOT(transfer_to_handler);			\
 	mtlr	r3;						\
 	addi	r3,r1,STACK_FRAME_OVERHEAD;			\