fix documentation for config_xxx.h files

Not that I know why the directory had to be renamed in the first place.

Change-Id: I3e4d07591876636ae4930240ac1acc68522fb94f

config_host/README

@@ -11,14 +11,14 @@ Adding a new setting:
 =====================
 
 - do AC_DEFINE(HAVE_FOO) in configure.ac when a setting should be set
-- choose the proper config/config_xxx.h file to use
+- choose the proper config_host/config_xxx.h file to use
     - if it is a global setting (such as availability of a compiler feature),
-        use config/config_global.h
-    - otherwise check if there is a matching config/config_hxx.h file
+        use config_host/config_global.h
+    - otherwise check if there is a matching config_host/config_hxx.h file
     - if none matches, add a new one:
-        - add config/config_xxx.h.in here, with just #ifndef include guard
-        - add AC_CONFIG_HEADERS([config/config_xxx.h]) next to the others
+        - add config_host/config_xxx.h.in here, with just #ifndef include guard
+        - add AC_CONFIG_HEADERS([config_host/config_xxx.h]) next to the others
             in configure.ac
-        - add config_hxx.h to config/.gitignore
-- add #undef HAVE_FOO to the config/config_hxx.h , possibly with a comment
+        - add config_hxx.h to config_host/.gitignore
+- add #undef HAVE_FOO to the config_host/config_hxx.h , possibly with a comment
 - add #include <config_xxx.h> before any #ifdef HAVE_XXX in a source file