w1: Drop dm.h header file

This header file should not be included in other header files. Remove it
and use a forward declaration instead.

Signed-off-by: Simon Glass <sjg@chromium.org>

board/atmel/common/board.c

@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <dm.h>
 #include <env.h>
 #include <w1.h>
 #include <w1-eeprom.h>

cmd/w1.c

@@ -6,6 +6,7 @@
  */
 #include <common.h>
 #include <command.h>
+#include <dm.h>
 #include <w1.h>
 #include <w1-eeprom.h>
 #include <dm/device-internal.h>

include/w1.h

@@ -8,7 +8,7 @@
 #ifndef __W1_H
 #define __W1_H
 
-#include <dm.h>
+struct udevice;
 
 #define W1_FAMILY_DS24B33	0x23
 #define W1_FAMILY_DS2431	0x2d