fixed the type inconsistent with document.

Document say probs will have CV_64F type. But in effect, it has CV_32F type.
http://docs.opencv.org/3.0.0/d1/dfb/classcv_1_1ml_1_1EM.html#a2ea7da92a75bc7a7d665c241f547b9b9

modules/ml/src/em.cpp

@@ -161,7 +161,7 @@ public:
     {
         bool needprobs = _outputs.needed();
         Mat samples = _inputs.getMat(), probs, probsrow;
-        int ptype = CV_32F;
+        int ptype = CV_64F;
         float firstres = 0.f;
         int i, nsamples = samples.rows;
 
@@ -187,7 +187,7 @@ public:
 
     Vec2d predict2(InputArray _sample, OutputArray _probs) const
     {
-        int ptype = CV_32F;
+        int ptype = CV_64F;
         Mat sample = _sample.getMat();
         CV_Assert(isTrained());