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>

drivers/net/zynq_gem.c

@@ -25,6 +25,7 @@
 #include <asm/system.h>
 #include <asm/arch/hardware.h>
 #include <asm/arch/sys_proto.h>
+#include <linux/err.h>
 #include <linux/errno.h>
 
 /* Bit/mask specification */