Sync with sun3/locore.s rev 1.88:

> Pass a frame pointer to trap() rather than the 'entire frame' trick.  Gcc4
> was optimizing away modifications to the frame contents (it's not nice to
> trick gcc).  Pass the pointer as the first argument to reduce the number
> of places that would be changed otherwise.  Fixes the getcwd regression
> test on most m68k ports.
Fixes MMU fault panic in trap() on sun3x.

This should be pulled up to netbsd-4 too.

sys/arch/sun3/sun3x/locore.s

@@ -1,4 +1,4 @@
-/*	$NetBSD: locore.s,v 1.55 2007/05/18 10:18:26 tsutsui Exp $	*/
+/*	$NetBSD: locore.s,v 1.56 2007/07/20 22:26:29 tsutsui Exp $	*/
 
 /*
  * Copyright (c) 1980, 1990, 1993
@@ -572,8 +572,9 @@ Lrei1:
 	clrl	%sp@-			| VA == none
 	clrl	%sp@-			| code == none
 	movl	#T_ASTFLT,%sp@-		| type == async system trap
+	pea	%sp@(12)		| fp == address of trap frame
 	jbsr	_C_LABEL(trap)		| go handle it
-	lea	%sp@(12),%sp		| pop value args
+	lea	%sp@(16),%sp		| pop value args
 	movl	%sp@(FR_SP),%a0		| restore user SP
 	movl	%a0,%usp		|   from save area
 	movw	%sp@(FR_ADJ),%d0	| need to adjust stack?