lib.poptrie_lookup: fix bug where offset was not set correctly
lib.poptrie_lookup: fix bug where offset was not set correctly

...when using direct pointing with s ~= 18.

SnabbCo/snabbswitch,Igalia/snabb,snabbco/snabb,Igalia/snabb,Igalia/snabb,snabbco/snabb,eugeneia/snabb,alexandergall/snabbswitch,snabbco/snabb,eugeneia/snabb,eugeneia/snabb,Igalia/snabb,SnabbCo/snabbswitch,alexandergall/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,alexandergall/snabbswitch,eugeneia/snabb,eugeneia/snabb,alexandergall/snabbswitch,SnabbCo/snabbswitch,Igalia/snabb,eugeneia/snabb,Igalia/snabb,Igalia/snabb,alexandergall/snabbswitch,snabbco/snabb,eugeneia/snabb,Igalia/snabb,snabbco/snabb,snabbco/snabb,alexandergall/snabbswitch,alexandergall/snabbswitch,snabbco/snabb,eugeneia/snabb,SnabbCo/snabbswitch