PlayerComponent: exclude disabled RPI MMAL codecs from list

Now installedDecoderCodecs() won't include e.g. "vc1" if the the MMAL
VC1 decoder wasn't enabled by adding a license to config.txt.

This could be used by web to drop their own checkCodecSupport() calls.

src/player/PlayerComponent.cpp

@@ -999,7 +999,7 @@ QStringList PlayerComponent::installedDecoderCodecs()
 
   for (auto driver : installedCodecDrivers())
   {
-    if (driver.type == CodecType::Decoder)
+    if (driver.type == CodecType::Decoder && checkCodecSupport(driver.format))
       formats.append(Codecs::plexNameFromFF(driver.format));
   }