sandbox: Add more dummy cache functions

In order for cmd/cache.c to link we need to add dummy icache functions
to mirror the dummy dcache functions as well as another dcache flush
function.

Signed-off-by: Tom Rini <trini@konsulko.com>

arch/sandbox/cpu/cpu.c

@@ -335,6 +335,10 @@ int dcache_status(void)
 	return 1;
 }
 
+void flush_dcache_all(void)
+{
+}
+
 void flush_dcache_range(unsigned long start, unsigned long stop)
 {
 }
@@ -343,6 +347,19 @@ void invalidate_dcache_range(unsigned long start, unsigned long stop)
 {
 }
 
+void icache_enable(void)
+{
+}
+
+void icache_disable(void)
+{
+}
+
+int icache_status(void)
+{
+	return 1;
+}
+
 /**
  * setup_auto_tree() - Set up a basic device tree to allow sandbox to work
  *