dm: core: Create a new header file for 'compat' features

At present dm/device.h includes the linux-compatible features. This
requires including linux/compat.h which in turn includes a lot of headers.
One of these is malloc.h which we thus end up including in every file in
U-Boot. Apart from the inefficiency of this, it is problematic for sandbox
which needs to use the system malloc() in some files.

Move the compatibility features into a separate header file.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/libavb/avb_slot_verify.c b/lib/libavb/avb_slot_verify.c
index c0defdf..58baf52 100644
--- a/lib/libavb/avb_slot_verify.c
+++ b/lib/libavb/avb_slot_verify.c
@@ -14,6 +14,7 @@
 #include "avb_util.h"
 #include "avb_vbmeta_image.h"
 #include "avb_version.h"
+#include <malloc.h>
 
 /* Maximum number of partitions that can be loaded with avb_slot_verify(). */
 #define MAX_NUMBER_OF_LOADED_PARTITIONS 32