net: Drop dm.h header file from phy.h

This header file should not be included in other header files. Remove it
and use other headers and C inclusions instead.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/read.h b/include/dm/read.h
index b1a6108..487ec9e 100644
--- a/include/dm/read.h
+++ b/include/dm/read.h
@@ -11,6 +11,7 @@
 
 #include <linux/errno.h>
 
+#include <dm/device.h>
 #include <dm/fdtaddr.h>
 #include <dm/ofnode.h>
 #include <dm/uclass.h>