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/timer/ast_timer.c b/drivers/timer/ast_timer.c
index 21ffdbf..3838601 100644
--- a/drivers/timer/ast_timer.c
+++ b/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
diff --git a/drivers/timer/cadence-ttc.c b/drivers/timer/cadence-ttc.c
index 75263c5..ed48a14 100644
--- a/drivers/timer/cadence-ttc.c
+++ b/drivers/timer/cadence-ttc.c
@@ -8,6 +8,7 @@
 #include <errno.h>
 #include <timer.h>
 #include <asm/io.h>
+#include <linux/err.h>
 
 #define CNT_CNTRL_RESET		BIT(4)
 
diff --git a/drivers/timer/timer-uclass.c b/drivers/timer/timer-uclass.c
index 97a4c74..b619200 100644
--- a/drivers/timer/timer-uclass.c
+++ b/drivers/timer/timer-uclass.c
@@ -11,6 +11,7 @@
 #include <clk.h>
 #include <errno.h>
 #include <timer.h>
+#include <linux/err.h>
 
 DECLARE_GLOBAL_DATA_PTR;