meta-ibm: prep for new override syntax

Change-Id: I9116ed7260e369136acb39eec15075db2d4dbeba
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/meta-ibm/meta-romulus/recipes-phosphor/mboxd/mboxd_%.bbappend b/meta-ibm/meta-romulus/recipes-phosphor/mboxd/mboxd_%.bbappend
index 566fc6c..4e1ac75 100644
--- a/meta-ibm/meta-romulus/recipes-phosphor/mboxd/mboxd_%.bbappend
+++ b/meta-ibm/meta-romulus/recipes-phosphor/mboxd/mboxd_%.bbappend
@@ -1 +1 @@
-MBOXD_FLASH_SIZE_romulus = "64M"
+MBOXD_FLASH_SIZE:romulus = "64M"