stepconf: fixup the check_for_rt() function for uspace
stepconf: fixup the check_for_rt() function for uspace

Before this commit, stepconf's check_for_rt() function would not work
right on uspace builds.

This commit makes the check_for_rt() function work right on both RTAI
builds and uspace builds.

    * RTAI builds with RTAI kernel: succeed (is rt)

    * uspace build with rt-preempt kernel: succeed (is rt)

    * RTAI build with a non-RTAI kernel: fail (not rt)

    * uspace build with non-rt-preempt kernel: fail (not rt)

Signed-off-by: Sebastian Kuzminsky <62d754cc350e84d3b1c32ae79f976f5348e74a40@highlab.com>

bmwiedemann/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,ikcalB/linuxcnc-mirror,ikcalB/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,ikcalB/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,ikcalB/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror,bmwiedemann/linuxcnc-mirror