st/omx: Fix resource leak on OMX_ErrorNone

Avoid leaking buffer allocated for task if an error has occured.

Coverity id: 1213929
Signed-off-by: Robert Foss <robert.foss@collabora.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/gallium/state_trackers/omx/vid_enc.c

@@ -1152,6 +1152,7 @@ static OMX_ERRORTYPE vid_enc_EncodeFrame(omx_base_PortType *port, OMX_BUFFERHEAD
       /* ------- load input image into video buffer ---- */
       err = enc_LoadImage(port, buf, task->buf);
       if (err != OMX_ErrorNone)
+         FREE(task);
          return err;
    }