src/platforms/common: move to platforms/common

Script to update include paths:
for i in $(grep -rl 'include <px4_work_queue' src platforms); do sed -i 's/#include <px4_work_queue/#include <px4_platform_common\/px4_work_queue/' $i; done

src/modules/uORB/SubscriptionCallback.hpp

@@ -40,7 +40,7 @@
 
 #include <uORB/SubscriptionInterval.hpp>
 #include <containers/List.hpp>
-#include <px4_work_queue/WorkItem.hpp>
+#include <px4_platform_common/px4_work_queue/WorkItem.hpp>
 
 namespace uORB
 {