Fix a -Wparentheses-equality Clang warning in cap_libv4l.cpp.

modules/highgui/src/cap_libv4l.cpp

@@ -856,8 +856,7 @@ static int _capture_V4L (CvCaptureCAM_V4L *capture, char *deviceName)
 
    detect_v4l = try_init_v4l(capture, deviceName);
 
-   if ((detect_v4l == -1)
-       )
+   if (detect_v4l == -1)
    {
      fprintf (stderr, "HIGHGUI ERROR: V4L"
               ": device %s: Unable to open for READ ONLY\n", deviceName);
@@ -865,8 +864,7 @@ static int _capture_V4L (CvCaptureCAM_V4L *capture, char *deviceName)
      return -1;
    }
 
-   if ((detect_v4l <= 0)
-       )
+   if (detect_v4l <= 0)
    {
      fprintf (stderr, "HIGHGUI ERROR: V4L"
               ": device %s: Unable to query number of channels\n", deviceName);