Rr/rocdec doc update (#188)

* update rocdec user guide

* minor change

* addressed review comment

[ROCm/rocdecode commit: 37e2725fec]

projects/rocdecode/api/rocparser.h

@@ -258,8 +258,6 @@ typedef struct _RocdecParserParams {
     PFNVIDSEQUENCECALLBACK pfnSequenceCallback; /**< IN: Called before decoding frames and/or whenever there is a fmt change */
     PFNVIDDECODECALLBACK pfnDecodePicture;      /**< IN: Called when a picture is ready to be decoded (decode order)         */
     PFNVIDDISPLAYCALLBACK pfnDisplayPicture;    /**< IN: Called whenever a picture is ready to be displayed (display order)  */
-    //PFNVIDOPPOINTCALLBACK pfnGetOperatingPoint; /**< IN: Called from AV1 sequence header to get operating point of a AV1 
-    //                                                     scalable bitstream                                                  */
     PFNVIDSEIMSGCALLBACK pfnGetSEIMsg;          /**< IN: Called when all SEI messages are parsed for particular frame        */
     void *pvReserved2[5];                       /**< Reserved for future use - set to NULL                                   */
     RocdecVideoFormatEx *pExtVideoInfo;             /**< IN: [Optional] sequence header data from system layer                   */