Add IOCTL interface to uORBManager for nuttx protected/kernel build split

When building uORB for NuttX flat build, or for some other target, everything
works as before.

When building uORB for NuttX protected or kernel build, this does the following:
- The kernel side uORB library reigsters a boardctl handler for calls from userspace
  and services the boardctl_ioctls by calling the actual uORB functions
- For user mode binaries, the uORBManager acts as a proxy, making boardctl_ioctl calls to the
  kernel side
- The uORBDeviceNodes are always allocated in user heap for protected build, so that they
  are accessible from both kernel and user side. This is only for optimization, a few
  functions such as "is_advertised" get really heavy when called frequently via ioctl

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

platforms/common/uORB/uORBDeviceMaster.cpp

@@ -49,6 +49,10 @@
 #include <poll.h>
 #endif // PX4_QURT
 
+#if defined(__PX4_NUTTX)
+#include <nuttx/mm/mm.h>
+#endif
+
 uORB::DeviceMaster::DeviceMaster()
 {
 	px4_sem_init(&_lock, 0, 1);
@@ -111,7 +115,11 @@ int uORB::DeviceMaster::advertise(const struct orb_metadata *meta, bool is_adver
 
 		/* if we didn't get a device, that's bad, free the path too */
 		if (node == nullptr) {
+#if defined(__PX4_NUTTX) && !defined(CONFIG_BUILD_FLAT)
+			kmm_free((void *)devpath);
+#else
 			free((void *)devpath);
+#endif
 			return -ENOMEM;
 		}