PCI: ftpci100: Release the clock resources

Smatch reported:
1. drivers/pci/controller/pci-ftpci100.c:526 faraday_pci_probe() warn:
'clk' from clk_prepare_enable() not released on lines: 442,451,462,478,512,517.
2. drivers/pci/controller/pci-ftpci100.c:526 faraday_pci_probe() warn:
'p->bus_clk' from clk_prepare_enable() not released on lines: 451,462,478,512,517.

The clock resource is obtained by devm_clk_get(), and then
clk_prepare_enable() makes the clock resource ready for use. After that,
clk_disable_unprepare() should be called to release the clock resource
when it is no longer needed. However, while doing some error handling
in faraday_pci_probe(), clk_disable_unprepare() is not called to release
clk and p->bus_clk before returning. These return lines are exactly 442,
451, 462, 478, 512, 517.

Fix this warning by replacing devm_clk_get() with devm_clk_get_enabled(),
which is equivalent to devm_clk_get() + clk_prepare_enable(). And with
devm_clk_get_enabled(), the clock will automatically be disabled,
unprepared and freed when the device is unbound from the bus.

Link: https://lore.kernel.org/r/20230508043641.23807-1-yejunyan@hust.edu.cn
Fixes: b3c433e ("PCI: faraday: Fix wrong pointer passed to PTR_ERR()")
Fixes: 2eeb02b ("PCI: faraday: Add clock handling")
Fixes: 783a862 ("PCI: faraday: Use pci_parse_request_of_pci_ranges()")
Fixes: d3c68e0 ("PCI: faraday: Add Faraday Technology FTPCI100 PCI Host Bridge driver")
Fixes: f1e8bd2 ("PCI: faraday: Convert IRQ masking to raw PCI config accessors")
Signed-off-by: Junyan Ye <yejunyan@hust.edu.cn>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Dongliang Mu <dzm91@hust.edu.cn>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pci/controller/pci-ftpci100.c

@@ -429,22 +429,12 @@ static int faraday_pci_probe(struct platform_device *pdev)
 	p->dev = dev;
 
 	/* Retrieve and enable optional clocks */
-	clk = devm_clk_get(dev, "PCLK");
+	clk = devm_clk_get_enabled(dev, "PCLK");
 	if (IS_ERR(clk))
 		return PTR_ERR(clk);
-	ret = clk_prepare_enable(clk);
-	if (ret) {
-		dev_err(dev, "could not prepare PCLK\n");
-		return ret;
-	}
-	p->bus_clk = devm_clk_get(dev, "PCICLK");
+	p->bus_clk = devm_clk_get_enabled(dev, "PCICLK");
 	if (IS_ERR(p->bus_clk))
 		return PTR_ERR(p->bus_clk);
-	ret = clk_prepare_enable(p->bus_clk);
-	if (ret) {
-		dev_err(dev, "could not prepare PCICLK\n");
-		return ret;
-	}
 
 	p->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(p->base))