libcamera: controls: Simplify SFINAE template parameter

Just use `void` instead of `std::void_t<>`.

Signed-off-by: Barnabás Pőcze <barnabas.pocze@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/controls.h

@@ -43,7 +43,7 @@ enum ControlType {
 
 namespace details {
 
-template<typename T, typename = std::void_t<>>
+template<typename T, typename = void>
 struct control_type {
 };