Firestone: Update XML package to latest.

Fixes open-power/op-build#208.
diff --git a/openpower/package/firestone-xml/firestone.mk b/openpower/package/firestone-xml/firestone.mk
index 66622f7..68e6347 100644
--- a/openpower/package/firestone-xml/firestone.mk
+++ b/openpower/package/firestone-xml/firestone.mk
@@ -4,7 +4,7 @@
 #
 ################################################################################
 
-FIRESTONE_XML_VERSION ?= 44d46e5f009b51fd65594c0efe6bb4f2380d11b1
+FIRESTONE_XML_VERSION ?= 7ac1ae80d0f965d39bdee944f89ed5a118d2adc2
 FIRESTONE_XML_SITE ?= $(call github,open-power,firestone-xml,$(FIRESTONE_XML_VERSION))
 
 FIRESTONE_XML_LICENSE = Apache-2.0