process: style

We don't need to check if the parent is already set.
This is done already in the proc_reparent.

No functional behaviour changes intended.

MFC after:	1 month

sys/kern/sys_process.c

@@ -958,9 +958,7 @@ kern_ptrace(struct thread *td, int req, pid_t pid, void *addr, int data)
 		 * on a "detach".
 		 */
 		proc_set_traced(p, true);
-		if (p->p_pptr != td->td_proc) {
 		proc_reparent(p, td->td_proc, false);
-		}
 		CTR2(KTR_PTRACE, "PT_ATTACH: pid %d, oppid %d", p->p_pid,
 		    p->p_oppid);