AP_HAL_Linux: rename lttng define

Like others, use HAVE_ prefix and name it HAVE_LTTNG_UST to be the same
name as exported by pkg-config While at it remove wrong comment with
_HELLO_TP_H.

libraries/AP_HAL_Linux/Perf.cpp

@@ -15,7 +15,7 @@
  * You should have received a copy of the GNU General Public License along
  * with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-#if !defined(PERF_LTTNG)
+#ifndef HAVE_LTTNG_UST
 
 #include <limits.h>
 #include <time.h>

libraries/AP_HAL_Linux/Perf_Lttng.cpp

@@ -12,7 +12,7 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
-#if defined(PERF_LTTNG)
+#ifdef HAVE_LTTNG_UST
 
 #define TRACEPOINT_CREATE_PROBES
 #define TRACEPOINT_DEFINE

libraries/AP_HAL_Linux/Perf_Lttng_TracePoints.h

@@ -59,7 +59,7 @@ TRACEPOINT_EVENT(
     )
 )
 
-#endif /* _HELLO_TP_H */
+#endif
 
 #include <lttng/tracepoint-event.h>
 

mk/board_native.mk

@@ -34,10 +34,10 @@ COPTS           =   -ffunction-sections -fdata-sections -fsigned-char
 ASOPTS          =   -x assembler-with-cpp 
 
 # features: TODO detect dependecy and make them optional
-HAVE_LTTNG=
+HAVE_LTTNG_UST=
 
-ifeq ($(HAVE_LTTNG),1)
-DEFINES        += -DPERF_LTTNG=1
+ifeq ($(HAVE_LTTNG_UST),1)
+DEFINES        += -DHAVE_LTTNG_UST=1
 LIBS           += -llttng-ust -ldl
 endif