getty: comment out parity detection code; improve usage text

function                                             old     new   delta
packed_usage                                       28155   28191     +36
static.erase                                          12       -     -12
getty_main                                          1847    1621    -226
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/1 up/down: 36/-238)          Total: -202 bytes

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