mpc83xx: Make distinct MPC8313ERDB targets

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>
diff --git a/arch/powerpc/cpu/mpc83xx/Kconfig b/arch/powerpc/cpu/mpc83xx/Kconfig
index 29d84f3..ede98c7 100644
--- a/arch/powerpc/cpu/mpc83xx/Kconfig
+++ b/arch/powerpc/cpu/mpc83xx/Kconfig
@@ -29,8 +29,14 @@
 	select ARCH_MPC8308
 	select SYS_FSL_ERRATUM_ESDHC111
 
-config TARGET_MPC8313ERDB
-	bool "Support MPC8313ERDB"
+config TARGET_MPC8313ERDB_NOR
+	bool "Support MPC8313ERDB_NOR"
+	select ARCH_MPC8313
+	select BOARD_EARLY_INIT_F
+	select SUPPORT_SPL
+
+config TARGET_MPC8313ERDB_NAND
+	bool "Support MPC8313ERDB_NAND"
 	select ARCH_MPC8313
 	select BOARD_EARLY_INIT_F
 	select SUPPORT_SPL