fix(video): only list video devices with video capture capability

This change adds a check for the V4L2_CAP_VIDEO_CAPTURE capability of
the video device found on devfs. This will filter out 'metadata' device
nodes that may be present on devfs at some  /dev/videoN path.

Fixes #6276

src/platform/camera/v4l2.cpp

@@ -206,6 +206,7 @@ QVector<QPair<QString, QString>> v4l2::getDeviceList()
         ioctl(fd, VIDIOC_QUERYCAP, &caps);
         close(fd);
 
+        if (caps.device_caps & V4L2_CAP_VIDEO_CAPTURE)
             devices += {file, reinterpret_cast<const char*>(caps.card)};
     }
     return devices;