ipa: raspberrypi: Add sensitivity field to camera mode

We use the CamHelper class to initialise it to the usual value of 1.

The CamHelper's GetModeSensitivity method can be redefined to
implement a different behaviour for sensors that require it.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/raspberrypi/cam_helper.cpp

@@ -129,6 +129,17 @@ bool CamHelper::SensorEmbeddedDataPresent() const
 	return false;
 }
 
+double CamHelper::GetModeSensitivity([[maybe_unused]] const CameraMode &mode) const
+{
+	/*
+	 * Most sensors have the same sensitivity in every mode, but this
+	 * method can be overridden for those that do not. Note that it is
+	 * called before mode_ is set, so it must return the sensitivity
+	 * of the mode that is passed in.
+	 */
+	return 1.0;
+}
+
 unsigned int CamHelper::HideFramesStartup() const
 {
 	/*