fixed gpu performance tests:

used new CV_PERF_TEST_MAIN_WITH_IMPLS mechanism

modules/softcascade/perf/perf_main.cpp

@@ -41,5 +41,13 @@
 //M*/
 
 #include "perf_precomp.hpp"
+#include "opencv2/ts/gpu_perf.hpp"
 
-CV_PERF_TEST_MAIN(softcascade)
+static const char * impls[] = {
+#ifdef HAVE_CUDA
+    "cuda",
+#endif
+    "plain"
+};
+
+CV_PERF_TEST_MAIN_WITH_IMPLS(softcascade, impls, perf::printCudaInfo())