Provide a working hotplugd(8) attach example

Current example not only doesn't work but also hard-codes `ugen0` device name.

Fix whitespace while there.

tools/openbsd/attach

@@ -8,13 +8,12 @@ case $DEVCLASS in
 	# generic devices
 	case "$DEVNAME" in
 	ugen*)
-		BUSNAME=`usbdevs -v -d | egrep "Controller|$DEVNAME\$" | grep -B 1 ugen0$ | head -n 1 | sed -e 's,Controller ,,' -e 's,:$,,' `
-		echo $BUSNAME >  /var/run/${DEVNAME}.bus
+		BUSNAME=$(usbdevs -vv | egrep "Controller|$DEVNAME\$" | grep -B 1 "$DEVNAME\$" | awk -F'[ :]' '/^Controller/ { print $2 }')
+		echo $BUSNAME > /var/run/${DEVNAME}.bus
 		# probably our scanner
 		chgrp usb /dev/"$DEVNAME".*
 		chgrp usb /dev/"$BUSNAME"
 		;;
 	esac
-
-        ;;
+	;;
 esac