powerpc: MPC8548: Move CONFIG_MPC8548 to Kconfig option

Replace CONFIG_MPC8548 with ARCH_MPC8548 in Kconfig.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/arch/powerpc/include/asm/config_mpc85xx.h b/arch/powerpc/include/asm/config_mpc85xx.h
index 6d845e8..1b4844f 100644
--- a/arch/powerpc/include/asm/config_mpc85xx.h
+++ b/arch/powerpc/include/asm/config_mpc85xx.h
@@ -66,7 +66,7 @@
 #define CONFIG_SYS_CCSRBAR_DEFAULT	0xff700000
 #define CONFIG_SYS_FSL_ERRATUM_A005125
 
-#elif defined(CONFIG_MPC8548)
+#elif defined(CONFIG_ARCH_MPC8548)
 #define CONFIG_MAX_CPUS			1
 #define CONFIG_SYS_FSL_NUM_LAWS		10
 #define CONFIG_SYS_FSL_DDRC_GEN2