dm: core: Require users of devres to include the header

At present devres.h is included in all files that include dm.h but few
make use of it. Also this pulls in linux/compat which adds several more
headers. Drop the automatic inclusion and require files to include devres
themselves. This provides a good indication of which files use devres.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
diff --git a/test/dm/syscon.c b/test/dm/syscon.c
index 0ff9da7..f1021f3 100644
--- a/test/dm/syscon.c
+++ b/test/dm/syscon.c
@@ -9,6 +9,7 @@
 #include <regmap.h>
 #include <asm/test.h>
 #include <dm/test.h>
+#include <linux/err.h>
 #include <test/ut.h>
 
 /* Base test of system controllers */