powctl: implement client api (needs board-specific impl)

libraries/libvapours/include/vapours/results.hpp

@@ -46,6 +46,7 @@
 #include <vapours/results/pcv_results.hpp>
 #include <vapours/results/pgl_results.hpp>
 #include <vapours/results/pm_results.hpp>
+#include <vapours/results/powctl_results.hpp>
 #include <vapours/results/psc_results.hpp>
 #include <vapours/results/pwm_results.hpp>
 #include <vapours/results/ro_results.hpp>