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/arch/arm/mach-rockchip/rk3368/clk_rk3368.c b/arch/arm/mach-rockchip/rk3368/clk_rk3368.c
index 55e5dd7..9a33c67 100644
--- a/arch/arm/mach-rockchip/rk3368/clk_rk3368.c
+++ b/arch/arm/mach-rockchip/rk3368/clk_rk3368.c
@@ -9,6 +9,7 @@
 #include <syscon.h>
 #include <asm/arch-rockchip/clock.h>
 #include <asm/arch-rockchip/cru_rk3368.h>
+#include <linux/err.h>
 
 int rockchip_get_clk(struct udevice **devp)
 {