dm: core: device: add function: dev_get_driver_ops()

This commit extends the driver model device's API by function:
- dev_get_driver_ops()

And this function returns the device's driver's operations if given:
- dev pointer, is non-NULL
- dev->driver->ops pointer, is non-NULL
in other case the, the NULL pointer is returned.

Signed-off-by: Przemyslaw Marczak <p.marczak@samsung.com>
Cc: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/device.h b/include/dm/device.h
index ad002fe..049cb2f 100644
--- a/include/dm/device.h
+++ b/include/dm/device.h
@@ -280,6 +280,17 @@
  */
 ulong dev_get_driver_data(struct udevice *dev);
 
+/**
+ * dev_get_driver_ops() - get the device's driver's operations
+ *
+ * This checks that dev is not NULL, and returns the pointer to device's
+ * driver's operations.
+ *
+ * @dev:	Device to check
+ * @return void pointer to driver's operations or NULL for NULL-dev or NULL-ops
+ */
+const void *dev_get_driver_ops(struct udevice *dev);
+
 /*
  * device_get_uclass_id() - return the uclass ID of a device
  *