powerpc: T104XRDB: Split to T1040RDB and T1042RDB in Kconfig

Split ARCH_T104XRDB as ARCH_T1040RDB and ARCH_T1042RDB in Kconfig to
simplify config options.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/configs/T1042RDB_SECURE_BOOT_defconfig b/configs/T1042RDB_SECURE_BOOT_defconfig
index e9d4145..2558159 100644
--- a/configs/T1042RDB_SECURE_BOOT_defconfig
+++ b/configs/T1042RDB_SECURE_BOOT_defconfig
@@ -1,6 +1,6 @@
 CONFIG_PPC=y
 CONFIG_MPC85xx=y
-CONFIG_TARGET_T104XRDB=y
+CONFIG_TARGET_T1042RDB=y
 # CONFIG_SYS_MALLOC_F is not set
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y