pm:cpupower: Add missing powercap_set_enabled() stub function

There was a symbol listed in the powercap.h file that was not implemented.
Implement it with a stub return of 0.

Programs like SWIG require that functions that are defined in the
headers be implemented.

Fixes: c2294c14 ("cpupower: Introduce powercap intel-rapl library and powercap-info command")
Suggested-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: John B. Wyatt IV <jwyatt@redhat.com>
Signed-off-by: John B. Wyatt IV <sageofredondo@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/power/cpupower/lib/powercap.c

@@ -77,6 +77,14 @@ int powercap_get_enabled(int *mode)
 	return sysfs_get_enabled(path, mode);
 }
 
+/*
+ * TODO: implement function. Returns dummy 0 for now.
+ */
+int powercap_set_enabled(int mode)
+{
+	return 0;
+}
+
 /*
  * Hardcoded, because rapl is the only powercap implementation
 - * this needs to get more generic if more powercap implementations