cmd: Expose a Kconfig option to enable UBIFS commands

Create a new Kconfig entry to allow CMD_UBIFS selection from Kconfig and
add an hidden LZO option that can be selected by CMD_UBIFS.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Jagan Teki <jagan@openedev.com>
diff --git a/lib/Kconfig b/lib/Kconfig
index 1048068..a0d5d92 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -135,6 +135,8 @@
 	  frame format currently (2015) implemented in the Linux kernel
 	  (generated by 'lz4 -l'). The two formats are incompatible.
 
+config LZO
+	bool
 endmenu
 
 config ERRNO_STR