increase the mem_alignment size used for output image rgb memory allocation (#70)

[ROCm/rocjpeg commit: c92ba3d1c4]

projects/rocjpeg/samples/rocjpeg_samples_utils.h

@@ -620,7 +620,7 @@ public:
     }
 
 private:
-    static const int mem_alignment = 1024 * 1024;
+    static const int mem_alignment = 4 * 1024 * 1024;
     /**
      * @brief Shows the help message and exits.
      *