phosphor-software-manager: ubifs_layout package config

Add ubifs_layout package config and pass --enable-ubifs_layout
configuration option when ubi-fs distro feature is enabled.

Tested: Verify --enable-ubifs_layout is passed to
        phosphor-software-manager's config for Witherspoon;
        And it is not passed for Romulus.

Change-Id: I6daa0c565d2c2be980b6292e62654c0a86a69bbc
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/classes/phosphor-software-manager-ubi-fs.bbclass b/classes/phosphor-software-manager-ubi-fs.bbclass
index 0e62023..f11fcd0 100644
--- a/classes/phosphor-software-manager-ubi-fs.bbclass
+++ b/classes/phosphor-software-manager-ubi-fs.bbclass
@@ -1,5 +1,7 @@
 # UBI-specific configuration for the phosphor-manager-software package
 
+PACKAGECONFIG_append = " ubifs_layout"
+
 RDEPENDS_phosphor-software-manager-updater-ubi += " \
     bash \
     mtd-utils-ubifs \