meta-phosphor: bump OELAYOUT_ABI

The meta-poky and OE use `OELAYOUT_ABI = 15` now.  Update phosphor-base
accordingly.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If892b20c55355935991bf51be00f9cdefbeee99e
diff --git a/meta-phosphor/conf/distro/include/phosphor-base.inc b/meta-phosphor/conf/distro/include/phosphor-base.inc
index 6061fff..1238873 100644
--- a/meta-phosphor/conf/distro/include/phosphor-base.inc
+++ b/meta-phosphor/conf/distro/include/phosphor-base.inc
@@ -51,8 +51,7 @@
 # that breaks the format and have been previously discussed on the mailing list
 # with general agreement from the core team.
 #
-
-OELAYOUT_ABI = "12"
+OELAYOUT_ABI = "15"
 
 # QA check settings - a little stricter than the OE-Core defaults
 WARN_TO_ERROR_QA = "already-stripped compile-host-path install-host-path \