ntpd: and real handling for -N, show usage w/o options; trim text

ntpd: and real handling for -N, show usage w/o options; trim text

function                                             old     new   delta
ntp_init                                             317     348     +31
bb_msg_you_must_be_root                                -      17     +17
xsocket                                               66      76     +10
changepath                                           195     194      -1
bb_msg_perm_denied_are_you_root                       35      34      -1
send_tree                                            355     353      -2
count_lines                                           74      72      -2
must_be_root                                          17       -     -17
------------------------------------------------------------------------------
(add/remove: 1/1 grow/shrink: 2/4 up/down: 58/-23)             Total: 35 bytes
   text   data    bss    dec    hexfilename
 832873    441   7548 840862  cd49ebusybox_old
 832839    441   7548 840828  cd47cbusybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>