libbladeRF: [WIP] Removed unnecessary mutex acquisition in CyAPI probe()

Using open_device() is overkill, as we just want to open a device handle to
read member variables for VID, PID, and serial #; we're not writing to the
device.

*NOTE:* The CyAPI docs say that this will Close() the device first if
        needed. This may be a bogus "fix" for #364, if the already opened device
        handle is beings used when the probe() is called.

host/libraries/libbladeRF/src/backend/usb/cyapi.c

@@ -87,6 +87,7 @@ static inline struct stream_data * get_stream_data(struct bladerf_stream *s)
     return (struct stream_data *) s->backend_data;
 }
 
+
 static int open_device(CCyUSBDevice *dev, int instance, HANDLE *mutex)
 {
     int status = 0;
@@ -154,18 +155,18 @@ static bool device_matches_target(CCyUSBDevice *dev,
 static int cyapi_probe(backend_probe_target probe_target,
                        struct bladerf_devinfo_list *info_list)
 {
-    int status = 0;
     CCyUSBDevice *dev = new CCyUSBDevice(NULL, driver_guid);
     if (dev == NULL) {
         return BLADERF_ERR_MEM;
     }
 
-    for (int i = 0; i < dev->DeviceCount() && status == 0; i++) {
+    for (int i = 0; i < dev->DeviceCount(); i++) {
         struct bladerf_devinfo info;
-        HANDLE mutex;
+        bool opened;
+        int status;
 
-        status = open_device(dev, i, &mutex);
-        if (status == 0) {
+        opened = dev->Open(i);
+        if (opened) {
             if (device_matches_target(dev, probe_target)) {
                 const size_t max_serial = sizeof(info.serial) - 1;
                 info.instance = i;
@@ -175,7 +176,7 @@ static int cyapi_probe(backend_probe_target probe_target,
                 info.usb_bus = 0; /* CyAPI doesn't provide this */
                 info.backend = BLADERF_BACKEND_CYPRESS;
                 status = bladerf_devinfo_list_add(info_list, &info);
-                if (status) {
+                if (status != 0) {
                     log_error("Could not add device to list: %s\n",
                               bladerf_strerror(status));
                 } else {
@@ -185,12 +186,11 @@ static int cyapi_probe(backend_probe_target probe_target,
             }
 
             dev->Close();
-            CloseHandle(mutex);
         }
     }
 
     delete dev;
-    return status;
+    return 0;
 
 }