y2038: vdso: change time_t to __kernel_old_time_t

Only x86 uses the 'time' syscall in vdso, so change that to
__kernel_old_time_t as a preparation for removing 'time_t' and
'__kernel_time_t' later.

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/x86/entry/vsyscall/vsyscall_64.c

@@ -194,7 +194,7 @@ bool emulate_vsyscall(unsigned long error_code,
 		break;
 
 	case 1:
-		if (!write_ok_or_segv(regs->di, sizeof(time_t))) {
+		if (!write_ok_or_segv(regs->di, sizeof(__kernel_old_time_t))) {
 			ret = -EFAULT;
 			goto check_fault;
 		}