libcamera: controls: Default ControlList validator argument to nullptr

The ControlList constructor takes a validator pointer that can be null.
Set its default value to nullptr to simplify code in users of
ControlList.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Tested-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>

src/ipa/rkisp1/rkisp1.cpp

@@ -220,7 +220,7 @@ void IPARkISP1::setControls(unsigned int frame)
 
 void IPARkISP1::metadataReady(unsigned int frame, unsigned int aeState)
 {
-	ControlList ctrls(nullptr);
+	ControlList ctrls;
 
 	if (aeState)
 		ctrls.set(controls::AeLocked, aeState == 2);