rename CFG_ macros to CONFIG_SYS

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/doc/README.silent b/doc/README.silent
index 6772532..a26e3df 100644
--- a/doc/README.silent
+++ b/doc/README.silent
@@ -13,7 +13,7 @@
  - When the console devices have been initialized, "stdout" and
    "stderr" are set to "nulldev", so subsequent messages are
    suppressed automatically. Make sure to enable "nulldev" by
-   #defining CFG_DEVICE_NULLDEV in your board config file.
+   #defining CONFIG_SYS_DEVICE_NULLDEV in your board config file.
 
  - When booting a linux kernel, the "bootargs" are fixed up so that
    the argument "console=" will be in the command line, no matter how