Blitter: Change some informational virtual functions to member values

src/video/opengl.cpp

@@ -490,6 +490,7 @@ void SetupDebugOutput()
  */
 OpenGLBackend::OpenGLBackend() : cursor_cache(MAX_CACHED_CURSORS)
 {
+	this->SetIs32BppSupported(true);
 }
 
 /**

src/video/opengl.h

@@ -107,7 +107,6 @@ public:
 
 	/* SpriteEncoder */
 
-	bool Is32BppSupported() override { return true; }
 	uint GetSpriteAlignment() override { return 1u << (ZOOM_LVL_SPR_COUNT - 1); }
 	Sprite *Encode(const SpriteLoader::Sprite *sprite, AllocatorProc *allocator) override;
 };