touch: Allow setting the timestamp to -1.

[des]

Summary

Note that VFS internally interprets a timestamp of -1 as “do not set”,
so this has no effect, but at least touch won't incorrectly reject the
given date / time (1969-12-31 23:59:59 UTC) as invalid.

While here, fix some style issues.

MFC after: 1 week

[allanjude]

reviewed-by: allanjude

usr.bin/touch/touch.c

case SIOCDELMULTI:
                 trunk = TRUNK(ifv);
                 if (trunk != NULL) {
                         TRUNK_LOCK(trunk);
                         error = vlan_setmulti(ifp);
                         TRUNK_UNLOCK(trunk);
                 }
                 break;
 
-        case SIOCSIFCAP:
-                VLAN_LOCK();
-                if (TRUNK(ifv) != NULL) {
-                        p = PARENT(ifv);
-                        VLAN_UNLOCK();
-                        if ((p->if_type != IFT_ETHER) &&
-                            (ifr->ifr_reqcap & IFCAP_VLAN_HWTAGGING) == 0) {
-                                error = EINVAL;
-                                break;
-                        }
-                        error = (*p->if_ioctl)(p, cmd, data);
-                        if (error)
-                                break;
-                        /* Propogate vlan interface capabilities */
-                        vlan_trunk_capabilities(p);
-                } else {
-                        VLAN_UNLOCK();
-                        error = EINVAL;
-                }
-                break;
-
         default:
                 error = EINVAL;
                 break;
         }
 
         return (error);
 }