dm: include <dm/util.h> from drivers/core/util.c

Fix sparse warnings "... was not declared. Should it be static?"

Also, fix redefinition of dm_warn/dm_dbg.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/core/util.c b/drivers/core/util.c
index 5ceac8b..2e232d5 100644
--- a/drivers/core/util.c
+++ b/drivers/core/util.c
@@ -5,9 +5,11 @@
  */
 
 #include <common.h>
+#include <dm/util.h>
 #include <libfdt.h>
 #include <vsprintf.h>
 
+#ifdef CONFIG_DM_WARN
 void dm_warn(const char *fmt, ...)
 {
 	va_list args;
@@ -16,7 +18,9 @@
 	vprintf(fmt, args);
 	va_end(args);
 }
+#endif
 
+#ifdef DEBUG
 void dm_dbg(const char *fmt, ...)
 {
 	va_list args;
@@ -25,6 +29,7 @@
 	vprintf(fmt, args);
 	va_end(args);
 }
+#endif
 
 int list_count_items(struct list_head *head)
 {