platform/x86: mlx-platform: Add physical bus number auto detection

mlx-platform does not provide a bus number to i2c-mlxcpld, assuming it
is always one. On some x86 systems, other i2c drivers may probe before
i2c-mlxcpld, causing bus one to be busy.

Make mlx-platform determine which adapter number is free prior to
activating i2c-mlxpld, adjusting the mux base numbers accordingly.
Update the mlxreg-hotplug pdata similarly.

This adds an explicit mlx-platform build dependency on I2C, update the
Kconfig accordingly. Add the missing REGMAP dependency while we're at
it.

Signed-off-by: Vadim Pasternak <vadimp@mellanox.com>
[dvhart: Rewrite commit message more concisely]
[dvhart: Add build dependencies]
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/mellanox/mlxreg-hotplug.c

@@ -96,6 +96,8 @@ struct mlxreg_hotplug_priv_data {
 static int mlxreg_hotplug_device_create(struct mlxreg_hotplug_priv_data *priv,
 					struct mlxreg_core_data *data)
 {
+	struct mlxreg_core_hotplug_platform_data *pdata;
+
 	/*
 	 * Return if adapter number is negative. It could be in case hotplug
 	 * event is not associated with hotplug device.
@@ -103,10 +105,12 @@ static int mlxreg_hotplug_device_create(struct mlxreg_hotplug_priv_data *priv,
 	if (data->hpdev.nr < 0)
 		return 0;
 
-	data->hpdev.adapter = i2c_get_adapter(data->hpdev.nr);
+	pdata = dev_get_platdata(&priv->pdev->dev);
+	data->hpdev.adapter = i2c_get_adapter(data->hpdev.nr +
+					      pdata->shift_nr);
 	if (!data->hpdev.adapter) {
 		dev_err(priv->dev, "Failed to get adapter for bus %d\n",
-			data->hpdev.nr);
+			data->hpdev.nr + pdata->shift_nr);
 		return -EFAULT;
 	}
 
@@ -114,8 +118,8 @@ static int mlxreg_hotplug_device_create(struct mlxreg_hotplug_priv_data *priv,
 					    data->hpdev.brdinfo);
 	if (!data->hpdev.client) {
 		dev_err(priv->dev, "Failed to create client %s at bus %d at addr 0x%02x\n",
-			data->hpdev.brdinfo->type, data->hpdev.nr,
-			data->hpdev.brdinfo->addr);
+			data->hpdev.brdinfo->type, data->hpdev.nr +
+			pdata->shift_nr, data->hpdev.brdinfo->addr);
 
 		i2c_put_adapter(data->hpdev.adapter);
 		data->hpdev.adapter = NULL;