Fix no previous declaration warning on armv7l compile.

mythtv/libs/libmythtv/visualisations/goom/zoom_filter_mmx.cpp

@@ -137,7 +137,7 @@ int zoom_filter_mmx_supported () {
 void zoom_filter_mmx (int prevX, int prevY,
                       const unsigned int *expix1, unsigned int *expix2,
                       const int *brutS, const int *brutD, int buffratio,
-                      GoomCoefficients &precalCoef)
+                      const GoomCoefficients &precalCoef)
 {
     (void)prevX;
     (void)prevY;