powerpc: T102xRDB: Split as T1023RDB and T1024RDB

The defconfig files are separated. Splitting targets in Kconfig simplifies
config options.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1023RDB_NAND_defconfig b/configs/T1023RDB_NAND_defconfig
index fed2560..4da49b6c 100644
--- a/configs/T1023RDB_NAND_defconfig
+++ b/configs/T1023RDB_NAND_defconfig
@@ -7,7 +7,7 @@
 CONFIG_SPL_ENV_SUPPORT=y
 CONFIG_SPL_DRIVERS_MISC_SUPPORT=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_T102XRDB=y
+CONFIG_TARGET_T1023RDB=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y