Fix a segmentation fault on some samples when the memory type is 3 (OUT_SURFACE_MEM_NOT_MAPPED) and attempting to save the output (which is not supported) (#239)

* Fix a segmentation fault on some samples when the memory type is 3 (OUT_SURFACE_MEM_NOT_MAPPED) and attempting to save the output (which is not supported)

* update the videoDecodeMultiFiles sample

* update the readme for videoDecodeMultiFiles

* add comments

* use OUT_SURFACE_MEM_NOT_MAPPED instead of integer number 3

[ROCm/rocdecode commit: 31c7c7c104]

projects/rocdecode/samples/videoDecodePerf/README.md

@@ -33,5 +33,4 @@ make -j
                   -t <number of threads [optional - default:4]>
                   -d <Device ID (>= 0) [optional - default:0]>
                   -z <force_zero_latency - Decoded frames will be flushed out for display immediately [optional]>
-                  -m <output_surface_memory_type - decoded surface memory [optional - default: 0][0 : OUT_SURFACE_MEM_DEV_INTERNAL/ 1 : OUT_SURFACE_MEM_DEV_COPIED/ 2 : OUT_SURFACE_MEM_HOST_COPIED]>
 ```