MN10300: Allow some cacheflushes to be avoided if cache snooping is available

The AM34 core is able to do cache snooping, and so can skip some of the cache
flushing.

Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/arch/mn10300/Kconfig b/arch/mn10300/Kconfig
index 069e34d..21e2a53 100644
--- a/arch/mn10300/Kconfig
+++ b/arch/mn10300/Kconfig
@@ -18,6 +18,7 @@
 config AM34_2
 	def_bool n
 	select MN10300_HAS_ATOMIC_OPS_UNIT
+	select MN10300_HAS_CACHE_SNOOP
 
 config MMU
 	def_bool y