Add direct-access methods to the base Device class, so that there's a common way of talking to drivers regardless of which of the specialised classes they derive from.

Make the Device destructor public and virtual, so that arbitrary devices can be deleted. Likewise for classes that derive from it.

Make Device::init public so that arbitrary devices can be initialised after being returned by factories.

src/drivers/device/device.cpp

@@ -223,5 +223,22 @@ interrupt(int irq, void *context)
 	return OK;
 }
 
+int
+Device::read(unsigned offset, void *data, unsigned count)
+{
+	return -ENODEV;
+}
 
-} // namespace device
+int
+Device::write(unsigned offset, void *data, unsigned count)
+{
+	return -ENODEV;
+}
+
+int
+Device::ioctl(unsigned operation, unsigned &arg)
+{
+	return -ENODEV;
+}
+
+} // namespace device