powerpc: MPC8572: Remove macro CONFIG_MPC8572

Replace CONFIG_MPC8572 with ARCH_MPC8572 in Kconfig and clean up existing
macros.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/board/xes/common/Makefile b/board/xes/common/Makefile
index 65d321a..1b2ec5c 100644
--- a/board/xes/common/Makefile
+++ b/board/xes/common/Makefile
@@ -6,7 +6,7 @@
 #
 
 obj-$(CONFIG_FSL_PCI_INIT)	+= fsl_8xxx_pci.o
-obj-$(CONFIG_MPC8572)		+= fsl_8xxx_clk.o
+obj-$(CONFIG_ARCH_MPC8572)		+= fsl_8xxx_clk.o
 obj-$(CONFIG_MPC86xx)		+= fsl_8xxx_clk.o
 obj-$(CONFIG_P2020)		+= fsl_8xxx_clk.o
 obj-$(CONFIG_MPC85xx)		+= fsl_8xxx_misc.o board.o