va: correct the description of segment id map buffer for av1e

remove VAEncSegMapBufferAV1 which actually not used at all
because there are no enough information to describe how to
use it

attention: this change will impact backward compatiblility,
considering no one is using it. we could ignore this side effect

Signed-off-by: Carl Zhang <carl.zhang@intel.com>

va/va_enc_av1.h

@@ -428,19 +428,19 @@ typedef struct _VAEncSegParamAV1 {
  * #VAEncMacroblockMapBufferType and the driver as well as the underline encoder
  * should honor what is given by the app.
  */
-typedef struct _VAEncSegMapBufferAV1 {
-    /** \brief Segment map data size. */
-    uint32_t    segmentMapDataSize;
 
-    /**
-     * \brief Segment map.
-     * Size of this map is indicated by \ref segmentMapDataSize and each element
-     * in this map contains the segment id of a particular block.
-     * The element is indexed by raster scan order.
-     * The value of each entry should be in the range [0..7], inclusive.
-     */
-    uint8_t    *pSegmentMap;
-} VAEncSegMapBufferAV1;
+/**
+ * \brief AV1 Block Segmentation ID Buffer
+ *
+ * The application provides a buffer of VAEncMacroblockMapBufferType containing
+ * the initial segmentation id for each block, block size is specified by seg_id_block_size
+ * in VAEncPictureParameterBufferAV1, one byte each, in raster scan order.
+ * Rate control may reassign it.  For example, a 640x480 video, set_id_block_size is
+ * VA_SEGID_BLOCK_16X16 , the buffer has 1200 entries.
+ * The value of each entry should be in the range [0..7], inclusive.
+ * If segmentation is not enabled, the application does not need to provide it.
+ */
+
 
 typedef enum {
     /** \brief Identity transformation, 0-parameter. */