i2c: xiic: use numbered adapter registration

Switch from i2c_add_adapter() to i2c_add_numbered_adapter() to enable
platforms to specify fixed I2C bus numbers via the platform device ID.

This allows systems to maintain consistent bus numbering across reboots.
On platforms where the device ID is PLATFORM_DEVID_NONE (the default),
the adapter falls back to dynamic allocation, preserving backward
compatibility.

Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Link: https://lore.kernel.org/r/20260223-i2c-xiic-v12-6-b6c9ce4e4f3c@nexthop.ai

Author: abdurrahman-nexthop

drivers/i2c/busses/i2c-xiic.c

@@ -1451,6 +1451,7 @@ static int xiic_i2c_probe(struct platform_device *pdev)
 	/* hook up driver to tree */
 	platform_set_drvdata(pdev, i2c);
 	i2c->adap = xiic_adapter;
+	i2c->adap.nr = pdev->id;
 	i2c_set_adapdata(&i2c->adap, i2c);
 	i2c->adap.dev.parent = &pdev->dev;
 	device_set_node(&i2c->adap.dev, fwnode);
@@ -1507,7 +1508,7 @@ static int xiic_i2c_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, ret, "Cannot xiic_reinit\n");
 
 	/* add i2c adapter to i2c tree */
-	ret = i2c_add_adapter(&i2c->adap);
+	ret = i2c_add_numbered_adapter(&i2c->adap);
 	if (ret) {
 		xiic_deinit(i2c);
 		return ret;