cmake remove circular linking and reorganize

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

src/modules/sdlog2/CMakeLists.txt

@@ -42,6 +42,5 @@ px4_add_module(
 		sdlog2.c
 		logbuffer.c
 	DEPENDS
-		platforms__common
 	)
-# vim: set noet ft=cmake fenc=utf-8 ff=unix :
+

src/modules/sdlog2/logbuffer.h

@@ -44,7 +44,7 @@
 #define SDLOG2_RINGBUFFER_H_
 
 #include <stdbool.h>
-#include <systemlib/perf_counter.h>
+#include <perf/perf_counter.h>
 
 struct logbuffer_s {
 	// pointers and size are in bytes

src/modules/sdlog2/sdlog2.c

@@ -103,8 +103,8 @@
 #include <uORB/topics/task_stack_info.h>
 
 #include <systemlib/systemlib.h>
-#include <systemlib/param/param.h>
-#include <systemlib/perf_counter.h>
+#include <parameters/param.h>
+#include <perf/perf_counter.h>
 #include <systemlib/printload.h>
 #include <systemlib/mavlink_log.h>
 #include <version/version.h>