initramfs-image-bundle: Add MTD_UBI

CONFIG_UBIFS_FS is used as 'm' in defconfig and depends on MTD and MTD_UBI which
is also 'm', inorder for it to include in kernel proper, set MTD_UBI=y
and MTD=y as well.

Signed-off-by: Khem Raj <raj.khem@gmail.com>

recipes-kernel/linux/files/initramfs-image-bundle.cfg

@@ -1,3 +1,5 @@
 CONFIG_OVERLAY_FS=y
 CONFIG_SQUASHFS=y
+CONFIG_MTD=y
+CONFIG_MTD_UBI=y
 CONFIG_UBIFS_FS=y