libcamera: Use utils::to_underlying()

Replace manual implementations of the utils::to_underlying() helper with
calls to the function.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>

src/libcamera/stream.cpp

@@ -433,7 +433,7 @@ std::ostream &operator<<(std::ostream &out, StreamRole role)
 		"Viewfinder",
 	};
 
-	out << names[static_cast<std::underlying_type_t<StreamRole>>(role)];
+	out << names[utils::to_underlying(role)];
 	return out;
 }