lavfi doxy: add buffer{src,sink}.h to the main lavfi doxy group

libavfilter/buffersink.h

@@ -21,11 +21,18 @@
 
 /**
  * @file
+ * @ingroup lavfi_buffersink
  * memory buffer sink API
  */
 
 #include "avfilter.h"
 
+/**
+ * @defgroup lavfi_buffersink Buffer sink API
+ * @ingroup lavfi
+ * @{
+ */
+
 #if FF_API_AVFILTERBUFFER
 /**
  * Get a buffer with filtered data from sink and put it in buf.
@@ -98,4 +105,8 @@ int av_buffersink_get_frame(AVFilterContext *ctx, AVFrame *frame);
  */
 int av_buffersink_get_samples(AVFilterContext *ctx, AVFrame *frame, int nb_samples);
 
+/**
+ * @}
+ */
+
 #endif /* AVFILTER_BUFFERSINK_H */

libavfilter/buffersrc.h

@@ -22,11 +22,18 @@
 
 /**
  * @file
+ * @ingroup lavfi_buffersrc
  * Memory buffer source API.
  */
 
 #include "avfilter.h"
 
+/**
+ * @defgroup lavfi_buffersrc Buffer source API
+ * @ingroup lavfi
+ * @{
+ */
+
 #if FF_API_AVFILTERBUFFER
 /**
  * Add a buffer to a filtergraph.
@@ -71,4 +78,8 @@ int av_buffersrc_write_frame(AVFilterContext *ctx, const AVFrame *frame);
  */
 int av_buffersrc_add_frame(AVFilterContext *ctx, AVFrame *frame);
 
+/**
+ * @}
+ */
+
 #endif /* AVFILTER_BUFFERSRC_H */