make the sparse method give correct results on CPU ocl

Add CL_CPU to supportsFeature check
simplify the logic of pyrlk

modules/ocl/include/opencv2/ocl/ocl.hpp

@@ -155,7 +155,7 @@ namespace cv
             static Context* getContext();
             static void setContext(Info &oclinfo);
 
-            enum {CL_DOUBLE, CL_UNIFIED_MEM};
+            enum {CL_DOUBLE, CL_UNIFIED_MEM, CL_CPU};
             bool supportsFeature(int ftype);
             size_t computeUnits();
             void* oclContext();

modules/ocl/src/initialization.cpp

@@ -979,6 +979,12 @@ namespace cv
                 return impl->double_support == 1;
             case CL_UNIFIED_MEM:
                 return impl->unified_memory == 1;
+            case CL_CPU:
+                cl_device_type devicetype;
+                clGetDeviceInfo(impl->devices[impl->devnum], 
+                                CL_DEVICE_TYPE, sizeof(cl_device_type), 
+                                &devicetype, NULL);
+                return devicetype == CVCL_DEVICE_TYPE_CPU;
             default:
                 return false;
             }

modules/ocl/src/matrix_operations.cpp

@@ -394,7 +394,7 @@ void cv::ocl::oclMat::convertTo( oclMat &dst, int rtype, double alpha, double be
     if( rtype < 0 )
         rtype = type();
     else
-        rtype = CV_MAKETYPE(CV_MAT_DEPTH(rtype), channels());
+        rtype = CV_MAKETYPE(CV_MAT_DEPTH(rtype), oclchannels());
 
     //int scn = channels();
     int sdepth = depth(), ddepth = CV_MAT_DEPTH(rtype);