Fix incorrect negative DAC output on STG cards
Fix incorrect negative DAC output on STG cards

Before this change, commanding full scale negative (-10.0) would
actually output +10.0 on the DAC.

ianmcmahon/linuxcnc-mirror,ArcEye/machinekit-testing,ianmcmahon/linuxcnc-mirror,Cid427/machinekit,ikcalB/linuxcnc-mirror,unseenlaser/machinekit,unseenlaser/machinekit,RunningLight/machinekit,cdsteinkuehler/linuxcnc,EqAfrica/machinekit,cdsteinkuehler/linuxcnc,araisrobo/linuxcnc,ArcEye/machinekit-testing,EqAfrica/machinekit,ianmcmahon/linuxcnc-mirror,araisrobo/machinekit,kinsamanka/machinekit,bmwiedemann/linuxcnc-mirror,cdsteinkuehler/linuxcnc,bobvanderlinden/machinekit,Cid427/machinekit,ikcalB/linuxcnc-mirror,ianmcmahon/linuxcnc-mirror,cnc-club/linuxcnc,ArcEye/machinekit-testing,mhaberler/machinekit,unseenlaser/machinekit,bobvanderlinden/machinekit,narogon/linuxcnc,ArcEye/MK-Qt5,cnc-club/linuxcnc,Cid427/machinekit,narogon/linuxcnc,ArcEye/machinekit-testing,bobvanderlinden/machinekit,Cid427/machinekit,strahlex/machinekit,unseenlaser/machinekit,ikcalB/linuxcnc-mirror,ArcEye/machinekit-testing,araisrobo/linuxcnc,kinsamanka/machinekit,cdsteinkuehler/MachineKit,araisrobo/machinekit,RunningLight/machinekit,jaguarcat79/ILC-with-LinuxCNC,mhaberler/machinekit,narogon/linuxcnc,cnc-club/linuxcnc,cnc-club/linuxcnc,RunningLight/machinekit,EqAfrica/machinekit,unseenlaser/machinekit,unseenlaser/linuxcnc,aschiffler/linuxcnc,jaguarcat79/ILC-with-LinuxCNC,cnc-club/linuxcnc,araisrobo/linuxcnc,ianmcmahon/linuxcnc-mirror,strahlex/machinekit,bmwiedemann/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,kinsamanka/machinekit,strahlex/machinekit,unseenlaser/linuxcnc,mhaberler/machinekit,ianmcmahon/linuxcnc-mirror,ikcalB/linuxcnc-mirror,kinsamanka/machinekit,araisrobo/machinekit,ArcEye/machinekit-testing,Cid427/machinekit,mhaberler/machinekit,unseenlaser/linuxcnc,RunningLight/machinekit,unseenlaser/linuxcnc,ikcalB/linuxcnc-mirror,jaguarcat79/ILC-with-LinuxCNC,strahlex/machinekit,ikcalB/linuxcnc-mirror,bobvanderlinden/machinekit,aschiffler/linuxcnc,cdsteinkuehler/MachineKit,aschiffler/linuxcnc,mhaberler/machinekit,Cid427/machinekit,kinsamanka/machinekit,araisrobo/machinekit,strahlex/machinekit,cdsteinkuehler/linuxcnc,cdsteinkuehler/linuxcnc,EqAfrica/machinekit,araisrobo/machinekit,unseenlaser/machinekit,ArcEye/MK-Qt5,bobvanderlinden/machinekit,araisrobo/linuxcnc,mhaberler/machinekit,araisrobo/machinekit,EqAfrica/machinekit,kinsamanka/machinekit,cdsteinkuehler/linuxcnc,mhaberler/machinekit,ArcEye/MK-Qt5,ArcEye/machinekit-testing,araisrobo/machinekit,ikcalB/linuxcnc-mirror,strahlex/machinekit,Cid427/machinekit,EqAfrica/machinekit,bmwiedemann/linuxcnc-mirror,ianmcmahon/linuxcnc-mirror,kinsamanka/machinekit,ArcEye/MK-Qt5,narogon/linuxcnc,unseenlaser/machinekit,bobvanderlinden/machinekit,aschiffler/linuxcnc,bobvanderlinden/machinekit,bmwiedemann/linuxcnc-mirror,strahlex/machinekit,araisrobo/machinekit,mhaberler/machinekit,RunningLight/machinekit,RunningLight/machinekit,kinsamanka/machinekit,ArcEye/MK-Qt5,aschiffler/linuxcnc,ArcEye/MK-Qt5,ArcEye/MK-Qt5,RunningLight/machinekit,ArcEye/MK-Qt5,cdsteinkuehler/MachineKit,bobvanderlinden/machinekit,unseenlaser/machinekit,cdsteinkuehler/MachineKit,narogon/linuxcnc,cdsteinkuehler/MachineKit,ArcEye/machinekit-testing,cdsteinkuehler/MachineKit,jaguarcat79/ILC-with-LinuxCNC,araisrobo/linuxcnc,araisrobo/machinekit,EqAfrica/machinekit,cnc-club/linuxcnc,Cid427/machinekit,bmwiedemann/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,EqAfrica/machinekit,jaguarcat79/ILC-with-LinuxCNC,unseenlaser/linuxcnc,RunningLight/machinekit,cnc-club/linuxcnc