powerpc: T1042D4RDB: Separate from T1042RDB in Kconfig

Use TARGET_T1042D4RDB in Kconfig to simplify config options.
Remove macro CONFIG_T1042D4RDB.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/powerpc/cpu/mpc85xx/Kconfig b/arch/powerpc/cpu/mpc85xx/Kconfig
index 980439e..9206b9b 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -230,6 +230,12 @@
 	select SUPPORT_SPL
 	select PHYS_64BIT
 
+config TARGET_T1042D4RDB
+	bool "Support T1042D4RDB"
+	select ARCH_T1042
+	select SUPPORT_SPL
+	select PHYS_64BIT
+
 config TARGET_T1042RDB_PI
 	bool "Support T1042RDB_PI"
 	select ARCH_T1042