cmake remove circular linking and reorganize

- px4_add_module now requires MAIN
 - px4_add_library doesn't automatically link

src/modules/mc_att_control/CMakeLists.txt

@@ -39,4 +39,6 @@ px4_add_module(
 	COMPILE_FLAGS
 	SRCS
 		mc_att_control_main.cpp
+	DEPENDS
+		mathlib
 	)

src/modules/mc_att_control/mc_att_control.hpp

@@ -34,7 +34,7 @@
 #include <lib/mixer/mixer.h>
 #include <mathlib/math/filter/LowPassFilter2p.hpp>
 #include <matrix/matrix/math.hpp>
-#include <systemlib/perf_counter.h>
+#include <perf/perf_counter.h>
 #include <px4_config.h>
 #include <px4_defines.h>
 #include <px4_module.h>