skiboot-5.3.0-rc1 for firenze, garrison and p9_mambo

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/openpower/configs/firenze_defconfig b/openpower/configs/firenze_defconfig
index c8a645a..e884d55 100644
--- a/openpower/configs/firenze_defconfig
+++ b/openpower/configs/firenze_defconfig
@@ -25,6 +25,8 @@
 # skiboot will be built but we don't need embedded payload
 BR2_PACKAGE_SKIBOOT=y
 BR2_PACKAGE_SKIBOOT_EMBED_PAYLOAD=n
+BR2_SKIBOOT_CUSTOM_VERSION=y
+BR2_SKIBOOT_CUSTOM_VERSION_VALUE="skiboot-5.3.0-rc1"
 
 # petitboot requirements
 BR2_ENABLE_LOCALE_PURGE=y