CONFIG_MPC8313ERDB is unused, and
TARGET_MPC8313ERDB_NAND/TARGET_MPC8313ERDB_NOR Kconfig could replace it.
Hence, get rid of CONFIG_MPC8313ERDB.
Signed-off-by: Mario Six <mario.six@gdsys.cc>
MPC8313ERDB has the option of either enabling NOR or NAND boot in its
config file (by commenting out certain #ifdefs). To keep this ability
after migrating options to Kconfig, we introduce two MPC8313ERDB
configs: one for NOR, and one for NAND.
Signed-off-by: Mario Six <mario.six@gdsys.cc>