Fix the performance issue introduced after PR#192 (#220)

* Fix the performance issue introduced after PR#192

* Destroy the current interop memories before reconfiguration

* initialize the interop to 0 after unmapping a surface

* code clean up

* check the mapped device mem/ext mem to be valid before destrying them

* code cleanup - add some comments

* make changes based on the reviewer comments

src/rocdecode/vaapi/vaapi_videodecoder.h

@@ -50,6 +50,7 @@ public:
     rocDecStatus SubmitDecode(RocdecPicParams *pPicParams);
     rocDecStatus GetDecodeStatus(int pic_idx, RocdecDecodeStatus* decode_status);
     rocDecStatus ExportSurface(int pic_idx, VADRMPRIMESurfaceDescriptor &va_drm_prime_surface_desc);
+    rocDecStatus SyncSurface(int pic_idx);
     rocDecStatus ReconfigureDecoder(RocdecReconfigureDecoderInfo *reconfig_params);
 private:
     RocDecoderCreateInfo decoder_create_info_;