busybox

vconfig: fix help text; small code shrink. Closes 4658

function                                             old     new   delta
xfind_str                                             45      46      +1
vconfig_main                                         228     223      -5
packed_usage                                       28980   28954     -26

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