powerpc: B4860: Remove macro CONFIG_PPC_B4860

Replace CONFIG_PPC_B4860 with ARCH_B4860 in Kconfig and clean up
existing macros.

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 23ee8f9..5b6dcad 100644
--- a/arch/powerpc/include/asm/config_mpc85xx.h
+++ b/arch/powerpc/include/asm/config_mpc85xx.h
@@ -611,7 +611,7 @@
 #define CONFIG_SYS_FSL_SFP_VER_3_0
 #define CONFIG_SYS_FSL_PCI_VER_3_X
 
-#elif defined(CONFIG_PPC_B4860) || defined(CONFIG_PPC_B4420)
+#elif defined(CONFIG_ARCH_B4860) || defined(CONFIG_PPC_B4420)
 #define CONFIG_E6500
 #define CONFIG_SYS_PPC64		/* 64-bit core */
 #define CONFIG_FSL_CORENET		/* Freescale CoreNet platform */
@@ -653,7 +653,7 @@
 #define CONFIG_SYS_CCSRBAR_DEFAULT	0xfe000000
 #define CONFIG_SYS_FSL_SFP_VER_3_0
 
-#ifdef CONFIG_PPC_B4860
+#ifdef CONFIG_ARCH_B4860
 #define CONFIG_SYS_FSL_CORES_PER_CLUSTER 4
 #define CONFIG_MAX_CPUS			4
 #define CONFIG_MAX_DSP_CPUS		12