connectx4: Move checkstatus() into post()
connectx4: Move checkstatus() into post()

Refactored the error checking to always be done when posting a command
to the command queue. Previously this was a manual step for each command
and that seems more error prone.

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