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/mm/Kconfig.cache b/arch/mn10300/mm/Kconfig.cache
index f5599f4..56a88dd 100644
--- a/arch/mn10300/mm/Kconfig.cache
+++ b/arch/mn10300/mm/Kconfig.cache
@@ -30,3 +30,6 @@
 	bool "Disabled"
 
 endchoice
+
+config MN10300_CACHE_ENABLED
+	def_bool y if !MN10300_CACHE_DISABLED