dm: core: Add a new flag to track platform data

We want to avoid allocating platform data twice. This could happen if
device_probe() is called after device_ofdata_to_platdata() for the same
device.

Add a flag to track whether device_ofdata_to_platdata() has been called on
a device. Check the flag to make sure it doesn't happen twice, and clear
the flag when the data is freed.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/device.h b/include/dm/device.h
index 2177470..9ebfd0a 100644
--- a/include/dm/device.h
+++ b/include/dm/device.h
@@ -65,6 +65,9 @@
 /* DM does not enable/disable the power domains corresponding to this device */
 #define DM_FLAG_DEFAULT_PD_CTRL_OFF	(1 << 11)
 
+/* Driver platdata has been read. Cleared when the device is removed */
+#define DM_FLAG_PLATDATA_VALID		(1 << 12)
+
 /*
  * One or multiple of these flags are passed to device_remove() so that
  * a selective device removal as specified by the remove-stage and the