libcamera: controls: Fix strict aliasing violation

gcc 8.3.0 for ARM complains about strict aliasing violations:

../../src/libcamera/controls.cpp: In member function ‘void libcamera::ControlValue::release()’:
../../src/libcamera/controls.cpp:111:13: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
   delete[] *reinterpret_cast<char **>(&storage_);

Fix it and simplify the code at the same time.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

include/libcamera/controls.h

@@ -160,7 +160,10 @@ private:
 	ControlType type_ : 8;
 	bool isArray_ : 1;
 	std::size_t numElements_ : 16;
-	uint64_t storage_;
+	union {
+		uint64_t value_;
+		void *storage_;
+	};
 
 	void release();
 	void set(ControlType type, bool isArray, const void *data,