powerpc: T1024: Remove macro CONFIG_PPC_T1024

Replace CONFIG_PPC_T1024 with ARCH_T1024 in Kconfig and clean up
existing macros.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/powerpc/cpu/mpc85xx/Kconfig b/arch/powerpc/cpu/mpc85xx/Kconfig
index 8e5461b..48447c9 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -191,6 +191,7 @@
 
 config TARGET_T1024QDS
 	bool "Support T1024QDS"
+	select ARCH_T1024
 	select SUPPORT_SPL
 	select PHYS_64BIT
 
@@ -202,6 +203,7 @@
 
 config TARGET_T1024RDB
 	bool "Support T1024RDB"
+	select ARCH_T1024
 	select SUPPORT_SPL
 	select PHYS_64BIT
 
@@ -358,6 +360,9 @@
 config ARCH_T1023
 	bool
 
+config ARCH_T1024
+	bool
+
 source "board/freescale/b4860qds/Kconfig"
 source "board/freescale/bsc9131rdb/Kconfig"
 source "board/freescale/bsc9132qds/Kconfig"