Fix comparing orb_metadata in uORB::DeviceNode::publish

Don't compare pointers to metadata, but the metadata contents.

In protected/kernel build there are two sets of metadata, on on kernel
side and another in user side. Thus the comparison of pointers would just
always fail. Compare orb_id instead

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

platforms/common/uORB/uORBDeviceNode.cpp

@@ -323,7 +323,7 @@ uORB::DeviceNode::publish(const orb_metadata *meta, orb_advert_t handle, const v
 	}
 
 	/* check if the orb meta data matches the publication */
-	if (devnode->_meta != meta) {
+	if (devnode->_meta->o_id != meta->o_id) {
 		errno = EINVAL;
 		return PX4_ERROR;
 	}