clearfog: mcp23s17: Use open-drain for IRQ sharing

This reflects a version of patch which was sent upstream and accepted.

Change-Id: Ibef230c4bc67ec79f5aec14cf1792a626ec4ce6a
diff --git a/board/czechlight/clearfog/czechlight-clearfog.dts b/board/czechlight/clearfog/czechlight-clearfog.dts
index 125e042..5b9620a 100644
--- a/board/czechlight/clearfog/czechlight-clearfog.dts
+++ b/board/czechlight/clearfog/czechlight-clearfog.dts
@@ -96,7 +96,7 @@
 		#gpio-cells = <2>;
 		microchip,spi-present-mask = <0x06>; /* extra addresses 1 and 2 */
 		microchip,irq-mirror;
-		microchip,irq-open-drain;
+		drive-open-drain;
 		spi-max-frequency = <10000000>;
 
 		gpio-line-names =