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/fdt.c b/arch/powerpc/cpu/mpc85xx/fdt.c
index 047c972..eeee92c 100644
--- a/arch/powerpc/cpu/mpc85xx/fdt.c
+++ b/arch/powerpc/cpu/mpc85xx/fdt.c
@@ -490,7 +490,7 @@
 }
 #endif
 
-#if defined(CONFIG_PPC_P4080)
+#if defined(CONFIG_ARCH_P4080)
 static void fdt_fixup_usb(void *fdt)
 {
 	ccsr_gur_t *gur = (void *)(CONFIG_SYS_MPC85xx_GUTS_ADDR);