mtd-utils: avoid to create two UBI_LAYOUT_VOLUME_ID volume

mtd-utils: avoid to create two UBI_LAYOUT_VOLUME_ID volume

When we create a ubi image by ubinize, a UBI_LAYOUT_VOLUME_ID
volume will be created by ubigen_write_layout_vol().
However, after the commit 4c00cf2c5816 (ubiformat: remove
no-volume-table option), ubiformat remove novtbl args in format().
As a result, it will also create a layout volume.

When we attempt to do ubiattach, it will fail for ubi_compare_lebs error:
ubi0 error: ubi_compare_lebs: unsupported on-flash UBI format
ubi0 error: ubi_attach_mtd_dev: failed to attach mtd1, error -22

Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>