powerpc: T4160RDB: Separate from T4240RDB in Kconfig

Use TARGET_T4160RDB to simplify Kconfig options.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/powerpc/cpu/mpc85xx/Kconfig b/arch/powerpc/cpu/mpc85xx/Kconfig
index d0fdceb..9d4e5ba 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -265,6 +265,11 @@
 	select SUPPORT_SPL
 	select PHYS_64BIT
 
+config TARGET_T4160RDB
+	bool "Support T4160RDB"
+	select SUPPORT_SPL
+	select PHYS_64BIT
+
 config TARGET_T4240QDS
 	bool "Support T4240QDS"
 	select SUPPORT_SPL