powerpc: P4080: Remove macro CONFIG_PPC_P4080

Replace CONFIG_PPC_P4080 with ARCH_P4080 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 d8bc1d0..a68a651 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -46,6 +46,7 @@
 config TARGET_P4080DS
 	bool "Support P4080DS"
 	select PHYS_64BIT
+	select ARCH_P4080
 
 config TARGET_P5020DS
 	bool "Support P5020DS"
@@ -320,6 +321,9 @@
 config ARCH_P3041
 	bool
 
+config ARCH_P4080
+	bool
+
 source "board/freescale/b4860qds/Kconfig"
 source "board/freescale/bsc9131rdb/Kconfig"
 source "board/freescale/bsc9132qds/Kconfig"