chpst: stop using data/bss

chpst: stop using data/bss

function                                             old     new   delta
chpst_main                                          1066    1089     +23
set_user                                               4       -      -4
root                                                   4       -      -4
nicelvl                                                4       -      -4
limitt                                                 4       -      -4
limits                                               196     192      -4
limitr                                                 4       -      -4
limitp                                                 4       -      -4
limito                                                 4       -      -4
limitl                                                 4       -      -4
limitf                                                 4       -      -4
limitd                                                 4       -      -4
limitc                                                 4       -      -4
limita                                                 4       -      -4
env_user                                               4       -      -4
env_dir                                                4       -      -4
------------------------------------------------------------------------------
(add/remove: 0/14 grow/shrink: 1/1 up/down: 23/-60)           Total: -37 bytes
   text    data     bss     dec     hex filename
 770892    1029    9520  781441   bec81 busybox_old
 770916     989    9496  781401   bec59 busybox_unstripped