PCI/ASPM: Use standard parsing functions for sysfs setters

The functions link_state_store() and clk_ctl_store() had just subtracted
ASCII '0' from input which could lead to undesired results.  Instead, use
Linux string functions to safely parse input.

[bhelgaas: check kstrtouint() return value]
Signed-off-by: Chris J Arges <chris.j.arges@canonical.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pcie/aspm.c

@@ -859,7 +859,10 @@ static ssize_t link_state_store(struct device *dev,
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
 	struct pcie_link_state *link, *root = pdev->link_state->root;
-	u32 val = buf[0] - '0', state = 0;
+	u32 val, state = 0;
+
+	if (kstrtouint(buf, 10, &val))
+		return -EINVAL;
 
 	if (aspm_disabled)
 		return -EPERM;
@@ -900,15 +903,14 @@ static ssize_t clk_ctl_store(struct device *dev,
 		size_t n)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	int state;
+	bool state;
 
-	if (n < 1)
+	if (strtobool(buf, &state))
 		return -EINVAL;
-	state = buf[0]-'0';
 
 	down_read(&pci_bus_sem);
 	mutex_lock(&aspm_lock);
-	pcie_set_clkpm_nocheck(pdev->link_state, !!state);
+	pcie_set_clkpm_nocheck(pdev->link_state, state);
 	mutex_unlock(&aspm_lock);
 	up_read(&pci_bus_sem);