powerpc: P1010: Remove macro CONFIG_P1010

Replace CONFIG_P1010 with ARCH_P1010 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 f4d9f9d..9b6dd34 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -96,6 +96,7 @@
 
 config TARGET_P1010RDB
 	bool "Support P1010RDB"
+	select ARCH_P1010
 	select SUPPORT_SPL
 	select SUPPORT_TPL
 
@@ -228,6 +229,9 @@
 config ARCH_MPC8572
 	bool
 
+config ARCH_P1010
+	bool
+
 source "board/freescale/b4860qds/Kconfig"
 source "board/freescale/bsc9131rdb/Kconfig"
 source "board/freescale/bsc9132qds/Kconfig"