dm: cache: Add enable and disable ops for sandbox and test

Add cache enable and disable ops for test coverage.

Signed-off-by: Rick Chen <rick@andestech.com>
Cc: KC Lin <kclin@andestech.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/test/dm/cache.c b/test/dm/cache.c
index d4144aa..2e244b1 100644
--- a/test/dm/cache.c
+++ b/test/dm/cache.c
@@ -14,6 +14,8 @@
 
 	ut_assertok(uclass_get_device(UCLASS_CACHE, 0, &dev_cache));
 	ut_assertok(cache_get_info(dev, &info));
+	ut_assertok(cache_enable(dev));
+	ut_assertok(cache_disable(dev));
 
 	return 0;
 }