hwmon: (pmbus) Virtualize pmbus_write_byte

With virtual pages and to be able to handle more chips, it is necessary to
virtualise pmbus_write_byte().

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
Reviewed-by: Robert Coulson <robert.coulson@ericsson.com>
diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index 0808d98..a6ae20f 100644
--- a/drivers/hwmon/pmbus/pmbus.h
+++ b/drivers/hwmon/pmbus/pmbus.h
@@ -325,6 +325,7 @@
 	int (*read_word_data)(struct i2c_client *client, int page, int reg);
 	int (*write_word_data)(struct i2c_client *client, int page, int reg,
 			       u16 word);
+	int (*write_byte)(struct i2c_client *client, int page, u8 value);
 	/*
 	 * The identify function determines supported PMBus functionality.
 	 * This function is only necessary if a chip driver supports multiple