Add support for the rocDecGetDecoderCaps API (#21)

* Add support for the rocDecGetDecoderCaps API

* move the RocDecVcnCodecSpec class to a new header file

src/rocdecode/roc_decoder.h

@@ -33,7 +33,6 @@ THE SOFTWARE.
 #include "../api/rocdecode.h"
 #include <hip/hip_runtime.h>
 
-
 class RocDecoder {
 public:
     RocDecoder(int device_id = 0);
@@ -47,10 +46,9 @@ public:
 private:
     rocDecStatus initHIP(int device_id);
     void initDRMnodes();
-
     int num_devices_;
     int device_id_;
     hipDeviceProp_t hip_dev_prop_;
     hipStream_t hip_stream_;
     std::vector<std::string> drm_nodes_;
-};
+};