openbmc: Switch RW FS from ext4 to jffs2

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/classes/image-overlay.bbclass b/classes/image-overlay.bbclass
index 1c6137d..8997aae 100644
--- a/classes/image-overlay.bbclass
+++ b/classes/image-overlay.bbclass
@@ -3,7 +3,7 @@
 INITRD ?= "${DEPLOY_DIR_IMAGE}/${INITRD_IMAGE}-${MACHINE}.cpio.${INITRD_CTYPE}${uboot}"
 
 IMAGE_BASETYPE ?= "squashfs-xz"
-OVERLAY_BASETYPE ?= "ext4"
+OVERLAY_BASETYPE ?= "jffs2"
 
 IMAGE_TYPES_${PN} += "${IMAGE_BASETYPE}"