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_defconfig b/configs/T1023RDB_defconfig
index c0fe36b..1c3510a 100644
--- a/configs/T1023RDB_defconfig
+++ b/configs/T1023RDB_defconfig
@@ -1,6 +1,6 @@
 CONFIG_PPC=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_T102XRDB=y
+CONFIG_TARGET_T1023RDB=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y