dm: core: Add dev_get_uclass_priv() to access uclass private data

Add a convenience function to access the private data that a uclass stores
for each of its devices. Convert over most existing uses for consistency
and to provide an example for others.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/device.h b/include/dm/device.h
index 7a48eb8..6980954 100644
--- a/include/dm/device.h
+++ b/include/dm/device.h
@@ -238,6 +238,16 @@
 struct udevice *dev_get_parent(struct udevice *child);
 
 /**
+ * dev_get_uclass_priv() - Get the private uclass data for a device
+ *
+ * This checks that dev is not NULL, but no other checks for now
+ *
+ * @dev		Device to check
+ * @return private uclass data for this device, or NULL if none
+ */
+void *dev_get_uclass_priv(struct udevice *dev);
+
+/**
  * dev_get_of_data() - get the device tree data used to bind a device
  *
  * When a device is bound using a device tree node, it matches a
diff --git a/include/i2c.h b/include/i2c.h
index 31b0389..6fd73fa 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -64,8 +64,8 @@
  * bus can operate at different speeds (measured in Hz, typically 100KHz
  * or 400KHz).
  *
- * To obtain this structure, use bus->uclass_priv where bus is the I2C
- * bus udevice.
+ * To obtain this structure, use dev_get_uclass_priv(bus) where bus is the
+ * I2C bus udevice.
  *
  * @speed_hz: Bus speed in hertz (typically 100000)
  */
@@ -340,7 +340,7 @@
 	 * The bus speed value will be updated by the uclass if this function
 	 * does not return an error. This method is optional - if it is not
 	 * provided then the driver can read the speed from
-	 * bus->uclass_priv->speed_hz
+	 * dev_get_uclass_priv(bus)->speed_hz
 	 *
 	 * @bus:	Bus to adjust
 	 * @speed:	Requested speed in Hz
@@ -354,7 +354,7 @@
 	 * Normally this can be provided by the uclass, but if you want your
 	 * driver to check the bus speed by looking at the hardware, you can
 	 * implement that here. This method is optional. This method would
-	 * normally be expected to return bus->uclass_priv->speed_hz.
+	 * normally be expected to return dev_get_uclass_priv(bus)->speed_hz.
 	 *
 	 * @bus:	Bus to check
 	 * @return speed of selected I2C bus in Hz, -ve on error