powerpc: P1023: Remove macro CONFIG_P1023

Replace CONFIG_P1023 with ARCH_P1023 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 4d9ffd3..0c498d8 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -114,6 +114,7 @@
 
 config TARGET_P1023RDB
 	bool "Support P1023RDB"
+	select ARCH_P1023
 
 config TARGET_P1_P2_RDB_PC
 	bool "Support p1_p2_rdb_pc"
@@ -243,6 +244,9 @@
 config ARCH_P1022
 	bool
 
+config ARCH_P1023
+	bool
+
 source "board/freescale/b4860qds/Kconfig"
 source "board/freescale/bsc9131rdb/Kconfig"
 source "board/freescale/bsc9132qds/Kconfig"