exit1(): Revert sparc64 workaround

If this still is a problem on other architectures, it should be fixed
properly.

This reverts commit 5486ffc898.

sys/kern/kern_exit.c

@@ -238,13 +238,7 @@ exit1(struct thread *td, int rval, int signo)
 	TSPROCEXIT(td->td_proc->p_pid);
 
 	p = td->td_proc;
-	/*
-	 * XXX in case we're rebooting we just let init die in order to
-	 * work around an unsolved stack overflow seen very late during
-	 * shutdown on sparc64 when the gmirror worker process exists.
-	 * XXX what to do now that sparc64 is gone... remove if?
-	 */
-	if (p == initproc && rebooting == 0) {
+	if (p == initproc) {
 		printf("init died (signal %d, exit %d)\n", signo, rval);
 		panic("Going nowhere without my init!");
 	}