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/drivers/ram/rockchip/dmc-rk3368.c b/drivers/ram/rockchip/dmc-rk3368.c
index 8addee8..2d82a17 100644
--- a/drivers/ram/rockchip/dmc-rk3368.c
+++ b/drivers/ram/rockchip/dmc-rk3368.c
@@ -19,6 +19,7 @@
 #include <asm/arch-rockchip/ddr_rk3368.h>
 #include <asm/arch-rockchip/sdram.h>
 #include <asm/arch-rockchip/sdram_rk3288.h>
+#include <linux/err.h>
 
 struct dram_info {
 	struct ram_info info;