hm2_pci: indicate failed registration to userspace
hm2_pci: indicate failed registration to userspace

Before this change, hm2_pci would still return success even if
no boards were registered, or if some boards failed registration.
This obscures the real problem, usually making the failed command
be a halcmd 'net' or 'setp' command for a hm2_pci pin or parameter.

Now, if zero boards are detected, or if at least one board encountered
a failure to register, rtapi_app_main will return a negative errno value
to indicate the problem, and halcmd will indicate the 'loadrt' line
as the cause of the problem.

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