In preparation of more renames, rename the variable that points to the
final users table.
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
[Thomas: as suggested by Arnout, use ROOTFS_FULL_USERS_TABLE instead
of ROOTFS_FINAL_USERS_TABLE.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>