replace <cfloat> with <float.h>

- <cfloat> isn't available in the NuttX c++ library

src/systemcmds/tests/test_controlmath.cpp

@@ -1,7 +1,7 @@
 #include <unit_test.h>
 #include <mc_pos_control/Utility/ControlMath.hpp>
 #include <mathlib/mathlib.h>
-#include <cfloat>
+#include <float.h>
 
 #define SIGMA_SINGLE_OP			0.000001f
 

src/systemcmds/tests/test_float.cpp

@@ -1,7 +1,7 @@
 #include <unit_test.h>
 
 #include <px4_config.h>
-#include <cfloat>
+#include <float.h>
 
 typedef union {
 	float f;