rv34_parser: Adjust #if for disabling individual parsers

As CONFIG_ values are always defined, they have to be checked via #if.

libavcodec/rv34_parser.c

@@ -76,7 +76,7 @@ static int rv34_parse(AVCodecParserContext *s,
     return buf_size;
 }
 
-#ifdef CONFIG_RV30_PARSER
+#if CONFIG_RV30_PARSER
 AVCodecParser ff_rv30_parser = {
     .codec_ids      = { AV_CODEC_ID_RV30 },
     .priv_data_size = sizeof(RV34ParseContext),
@@ -84,7 +84,7 @@ AVCodecParser ff_rv30_parser = {
 };
 #endif
 
-#ifdef CONFIG_RV40_PARSER
+#if CONFIG_RV40_PARSER
 AVCodecParser ff_rv40_parser = {
     .codec_ids      = { AV_CODEC_ID_RV40 },
     .priv_data_size = sizeof(RV34ParseContext),