mpc83xx: Introduce ARCH_MPC831*

Replace CONFIG_MPC833* with proper CONFIG_ARCH_MPC833* Kconfig options.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/arch/powerpc/cpu/mpc83xx/spd_sdram.c b/arch/powerpc/cpu/mpc83xx/spd_sdram.c
index 97ef771..3f18aad 100644
--- a/arch/powerpc/cpu/mpc83xx/spd_sdram.c
+++ b/arch/powerpc/cpu/mpc83xx/spd_sdram.c
@@ -31,7 +31,7 @@
 	printf(" (DDR%d", ((ddr->sdram_cfg & SDRAM_CFG_SDRAM_TYPE_MASK)
 			   >> SDRAM_CFG_SDRAM_TYPE_SHIFT) - 1);
 
-#if defined(CONFIG_ARCH_MPC8308) || defined(CONFIG_MPC831x)
+#if defined(CONFIG_ARCH_MPC8308) || defined(CONFIG_ARCH_MPC831X)
 	if ((ddr->sdram_cfg & SDRAM_CFG_DBW_MASK) == SDRAM_CFG_DBW_16)
 		puts(", 16-bit");
 	else if ((ddr->sdram_cfg & SDRAM_CFG_DBW_MASK) == SDRAM_CFG_DBW_32)