CCodec: Fix null check

'dst' is always non-null, by assumption of the function.  We need
to check if "*dst" is null or not.

We also update the interface definition.

Bug: 197719179
Test: TreeHugger
Change-Id: Ic86891f936f4e84241c55674c1aedcb0d7e15483
diff --git a/media/codec2/sfplugin/CCodecBuffers.h b/media/codec2/sfplugin/CCodecBuffers.h
index 7f3a655..c8e9930 100644
--- a/media/codec2/sfplugin/CCodecBuffers.h
+++ b/media/codec2/sfplugin/CCodecBuffers.h
@@ -385,7 +385,7 @@
     void submit(const sp<MediaCodecBuffer> &buffer);
 
     /**
-     * Apply DataConverter from |src| to |*dst| if needed. If |dst| is nullptr,
+     * Apply DataConverter from |src| to |*dst| if needed. If |*dst| is nullptr,
      * a new buffer is allocated.
      *
      * Returns true if conversion was needed and executed; false otherwise.