cmake remove circular linking and reorganize

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

src/drivers/distance_sensor/srf02/CMakeLists.txt

@@ -38,6 +38,5 @@ px4_add_module(
 	SRCS
 		srf02.cpp
 	DEPENDS
-		platforms__common
 	)
-# vim: set noet ft=cmake fenc=utf-8 ff=unix :
+

src/drivers/distance_sensor/srf02/srf02.cpp

@@ -58,7 +58,7 @@
 #include <unistd.h>
 #include <vector>
 
-#include <systemlib/perf_counter.h>
+#include <perf/perf_counter.h>
 #include <systemlib/err.h>
 
 #include <drivers/drv_hrt.h>