powerpc: mpc85xx: Convert CONFIG_SYS_CCSRBAR_DEFAULT to Kconfig option

Move default value definitions to to Kconfig SYS_CCSRBAR_DEFAULT.

Signed-off-by: York Sun <york.sun@nxp.com>
diff --git a/doc/README.ramboot-ppc85xx b/doc/README.ramboot-ppc85xx
index 5cc546a..c9fef53 100644
--- a/doc/README.ramboot-ppc85xx
+++ b/doc/README.ramboot-ppc85xx
@@ -90,8 +90,8 @@
 
    This will finally use the CONFIG_SYS_RAMBOOT.
 
-3. File name-> arch/powerpc/include/asm/config_mpc85xx.h
-   In the section of the particular SOC, for example P1020,
+3. Change CONFIG_SYS_CCSRBAR_DEFAULT in menuconfig accordingly.
+   In the section of the particular SOC, for example P1020, pseudo code
 
    #if defined(CONFIG_GO)
    #define CONFIG_SYS_CCSRBAR_DEFAULT	0xffe00000