t_signal_and_sp: contextsplink test may not be broken on n64.

n32 and n64 have the same stack alignment requirement (16-byte), so
if there were a problem it would probably manifest on n32 too.  But
the only things that __resumecontext does with a misaligned sp are:

1. syscall getcontext (not even via the syscall stub, but via the
   syscall instruction directly), which is unlikely to care; and

2. tail-call setcontext, which does a syscall (again, unlikely to
   care) that will discard the caller's sp and replace it altogether.

So I'm not sure we can even test potential adverse consequences of
misalignment inside __resumecontext, short of interposing our own
setcontext symbol to artificially verify its stack alignment before
passing on to the syscall -- which, while feasible, is maybe not
worth the effort.

PR kern/59327: user stack pointer is not aligned properly

Author: riastradh

tests/kernel/t_signal_and_sp.c

@@ -1,4 +1,4 @@
-/*	$NetBSD: t_signal_and_sp.c,v 1.11 2025/04/24 16:57:27 riastradh Exp $	*/
+/*	$NetBSD: t_signal_and_sp.c,v 1.12 2025/04/24 17:00:25 riastradh Exp $	*/
 
 /*
  * Copyright (c) 2024 The NetBSD Foundation, Inc.
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: t_signal_and_sp.c,v 1.11 2025/04/24 16:57:27 riastradh Exp $");
+__RCSID("$NetBSD: t_signal_and_sp.c,v 1.12 2025/04/24 17:00:25 riastradh Exp $");
 
 #include <sys/wait.h>
 
@@ -315,11 +315,6 @@ ATF_TC_BODY(contextsplink, tc)
 	fprintf(stderr, "stack2 @ [%p,%p)\n",
 	    stack2, stack2 + SIGSTKSZ + STACK_ALIGNBYTES);
 
-#ifdef __mips_n64
-	atf_tc_expect_fail("PR kern/59327:"
-	    " user stack pointer is not aligned properly");
-#endif
-
 	for (i = 0; i <= STACK_ALIGNBYTES; i++) {
 		contextsp = NULL;
 		test_context_done = false;