MN10300: Provide a MN10300_CACHE_ENABLED config option

Provide a MN10300_CACHE_ENABLED config option as inverted logic of
MN10300_CACHE_DISABLED to make things simpler.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/arch/mn10300/include/asm/gdb-stub.h b/arch/mn10300/include/asm/gdb-stub.h
index 41ed2676..f5495ad 100644
--- a/arch/mn10300/include/asm/gdb-stub.h
+++ b/arch/mn10300/include/asm/gdb-stub.h
@@ -110,7 +110,7 @@
 extern asmlinkage void __gdbstub_bug_trap(void);
 extern asmlinkage void __gdbstub_pause(void);
 
-#ifndef CONFIG_MN10300_CACHE_DISABLED
+#ifdef CONFIG_MN10300_CACHE_ENABLED
 extern asmlinkage void gdbstub_purge_cache(void);
 #else
 #define gdbstub_purge_cache()	do {} while (0)