mkconfig: change CONFIG_MK_ prefix into plain CONFIG_

When planning for more generalization and Makefile cleanup it became
obvious that the introduction of a separate CONFIG_MK_ name space for
config options that were set through scripting in the Makefile was
not a good idea.

Originally the idea was to provide a script-free approach to supply
configuration options - there was no real need for a separate name
space. But when we now convert the existing Makefile entries to make
use of this approach, it would mean that we have to touch a large
number of board config files and add #ifdef / #define sequences to
"convert" from the CONFIG_MK_ to the CONFIG_ name space.

It seems much cleaner to get rid of this somewhat arbitrary _MK
string now for the few boards that actually use it.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/include/configs/SBC8540.h b/include/configs/SBC8540.h
index d6b3cb8..688f8a2 100644
--- a/include/configs/SBC8540.h
+++ b/include/configs/SBC8540.h
@@ -34,7 +34,7 @@
 /*
  * Top level Makefile configuration choices
  */
-#ifdef CONFIG_MK_66
+#ifdef CONFIG_66
 #define CONFIG_PCI_66
 #endif