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/timer/ast_timer.c

@@ -9,6 +9,7 @@
 #include <timer.h>
 #include <asm/io.h>
 #include <asm/arch/timer.h>
+#include <linux/err.h>
 
 #define AST_TICK_TIMER  1
 #define AST_TMC_RELOAD_VAL  0xffffffff