backend: Remove protected members from the BackEnd class

This class will not be derived, so replace the protected definitions
with private ones.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>

src/libpisp/backend/backend.hpp

@@ -147,7 +147,7 @@ class BackEnd
 		return mutex_.try_lock();
 	}
 
-protected:
+private:
 	struct BeConfigExtra
 	{
 		// Non-register fields:
@@ -183,7 +183,6 @@ class BackEnd
 	std::vector<SmartResize> smart_resize_;
 	uint32_t smart_resize_dirty_;
 
-private:
 	// Default config
 	std::map<std::string, pisp_be_ccm_config> ycbcr_map_;
 	std::map<std::string, pisp_be_ccm_config> inverse_ycbcr_map_;