powerpc: P2041: Remove macro CONFIG_PPC_P2041

Replace CONFIG_PPC_P2041 with ARCH_P2041 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 51192fe..0ddb7c5 100644
--- a/arch/powerpc/cpu/mpc85xx/Kconfig
+++ b/arch/powerpc/cpu/mpc85xx/Kconfig
@@ -170,6 +170,7 @@
 
 config TARGET_P2041RDB
 	bool "Support P2041RDB"
+	select ARCH_P2041
 	select PHYS_64BIT
 
 config TARGET_QEMU_PPCE500
@@ -221,6 +222,7 @@
 
 config TARGET_KMP204X
 	bool "Support kmp204x"
+	select ARCH_P2041
 	select PHYS_64BIT
 
 config TARGET_XPEDITE520X
@@ -311,6 +313,9 @@
 config ARCH_P2020
 	bool
 
+config ARCH_P2041
+	bool
+
 source "board/freescale/b4860qds/Kconfig"
 source "board/freescale/bsc9131rdb/Kconfig"
 source "board/freescale/bsc9132qds/Kconfig"