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>

drivers/adc/stm32-adc.c

@@ -9,6 +9,7 @@
 #include <common.h>
 #include <adc.h>
 #include <asm/io.h>
+#include <dm/device_compat.h>
 #include <linux/iopoll.h>
 #include "stm32-adc-core.h"