clearfog: Enable IRQ for the built-in GPIO expander

Change-Id: I0a605998a20bbce23207aaa4f5d7ee3adccdc101
diff --git a/board/czechlight/clearfog/linux.fragment b/board/czechlight/clearfog/linux.fragment
index 1ea804e..2ccbf53 100644
--- a/board/czechlight/clearfog/linux.fragment
+++ b/board/czechlight/clearfog/linux.fragment
@@ -5,6 +5,9 @@
 CONFIG_MVNETA_BM_ENABLE=y
 CONFIG_MVPP2=n
 
+# Clearfog: enable interrupt signalling for the expander0
+CONFIG_GPIO_PCA953X_IRQ=y
+
 # PMBus for the PSUs
 CONFIG_PMBUS=y
 CONFIG_SENSORS_PMBUS=y