ggml-qnn: remove redundant functions in this PR and make codes more clear

Author: zhouwg

ggml/include/ggml-qnn.h

@@ -29,7 +29,7 @@ extern "C" {
 #endif
 
 #define GGML_QNN_MAX_DEVICES    3
-#define GGML_QNN_BACKEND_NAME   "qnn"
+#define GGML_QNN_BACKEND_NAME   "hexagon"
 
 enum QNNBackend {
     QNN_BACKEND_CPU,