nand: 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>
diff --git a/drivers/mtd/nand/raw/brcmnand/brcmnand_compat.h b/drivers/mtd/nand/raw/brcmnand/brcmnand_compat.h
index 6f9bec7..52711d4 100644
--- a/drivers/mtd/nand/raw/brcmnand/brcmnand_compat.h
+++ b/drivers/mtd/nand/raw/brcmnand/brcmnand_compat.h
@@ -3,8 +3,8 @@
 #ifndef __BRCMNAND_COMPAT_H
 #define __BRCMNAND_COMPAT_H
 
-#include <clk.h>
-#include <dm.h>
+struct clk;
+struct udevice;
 
 char *devm_kasprintf(struct udevice *dev, gfp_t gfp, const char *fmt, ...);