powerpc: T4160: Remove macro CONFIG_PPC_T4160

Use CONFIG_ARCH_T4160 instead.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/powerpc/cpu/mpc85xx/Kconfig b/arch/powerpc/cpu/mpc85xx/Kconfig
index 9d4e5ba..991127d 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -262,11 +262,13 @@
 
 config TARGET_T4160QDS
 	bool "Support T4160QDS"
+	select ARCH_T4160
 	select SUPPORT_SPL
 	select PHYS_64BIT
 
 config TARGET_T4160RDB
 	bool "Support T4160RDB"
+	select ARCH_T4160
 	select SUPPORT_SPL
 	select PHYS_64BIT
 
@@ -419,6 +421,9 @@
 config ARCH_T2081
 	bool
 
+config ARCH_T4160
+	bool
+
 source "board/freescale/b4860qds/Kconfig"
 source "board/freescale/bsc9131rdb/Kconfig"
 source "board/freescale/bsc9132qds/Kconfig"