spi: mt7621: Use the devm_clk_get_enabled() helper to simplify error handling

The devm_clk_get_enabled() helper:
   - calls devm_clk_get()
   - calls clk_prepare_enable() and registers what is needed in order to
     call clk_disable_unprepare() when needed, as a managed resource.

This helper is well suited for cases where the clock would be kept
prepared or enabled for the whole lifetime of the driver.

This simplifies the error handling a lot.

The order between spi_unregister_controller() (in the remove function) and
the clk_disable_unprepare() (now handle by a  managed resource) is kept
the same.
(see commit 46b5c4fb ("spi: mt7621: Don't leak SPI master in probe
error path") to see why it matters)
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/05a7fd22719008c8a905d6328aa9548ce40f2a7a.1661599671.git.christophe.jaillet@wanadoo.frSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-mt7621.c

@@ -327,7 +327,6 @@ static int mt7621_spi_probe(struct platform_device *pdev)
 	struct spi_controller *master;
 	struct mt7621_spi *rs;
 	void __iomem *base;
-	int status = 0;
 	struct clk *clk;
 	int ret;
 
@@ -339,19 +338,14 @@ static int mt7621_spi_probe(struct platform_device *pdev)
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
-	clk = devm_clk_get(&pdev->dev, NULL);
+	clk = devm_clk_get_enabled(&pdev->dev, NULL);
 	if (IS_ERR(clk))
 		return dev_err_probe(&pdev->dev, PTR_ERR(clk),
 				     "unable to get SYS clock\n");
 
-	status = clk_prepare_enable(clk);
-	if (status)
-		return status;
-
 	master = devm_spi_alloc_master(&pdev->dev, sizeof(*rs));
 	if (!master) {
 		dev_info(&pdev->dev, "master allocation failed\n");
-		clk_disable_unprepare(clk);
 		return -ENOMEM;
 	}
 
@@ -376,13 +370,10 @@ static int mt7621_spi_probe(struct platform_device *pdev)
 	ret = device_reset(&pdev->dev);
 	if (ret) {
 		dev_err(&pdev->dev, "SPI reset failed!\n");
-		clk_disable_unprepare(clk);
 		return ret;
 	}
 
 	ret = spi_register_controller(master);
-	if (ret)
-		clk_disable_unprepare(clk);
 
 	return ret;
 }
@@ -390,13 +381,10 @@ static int mt7621_spi_probe(struct platform_device *pdev)
 static int mt7621_spi_remove(struct platform_device *pdev)
 {
 	struct spi_controller *master;
-	struct mt7621_spi *rs;
 
 	master = dev_get_drvdata(&pdev->dev);
-	rs = spi_controller_get_devdata(master);
 
 	spi_unregister_controller(master);
-	clk_disable_unprepare(rs->clk);
 
 	return 0;
 }