Revert "ARM: amba: Fix race condition with driver_override"

This reverts commit 6b614a87.

My backport was incorrect, as Geert pointed out :(
Reported-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Cc: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/amba/bus.c

@@ -69,15 +69,11 @@ static ssize_t driver_override_show(struct device *_dev,
 				    struct device_attribute *attr, char *buf)
 {
 	struct amba_device *dev = to_amba_device(_dev);
-	ssize_t len;
 
 	if (!dev->driver_override)
 		return 0;
 
-	device_lock(_dev);
-	len = sprintf(buf, "%s\n", dev->driver_override);
-	device_unlock(_dev);
-	return len;
+	return sprintf(buf, "%s\n", dev->driver_override);
 }
 
 static ssize_t driver_override_store(struct device *_dev,
@@ -85,7 +81,7 @@ static ssize_t driver_override_store(struct device *_dev,
 				     const char *buf, size_t count)
 {
 	struct amba_device *dev = to_amba_device(_dev);
-	char *driver_override, *old, *cp;
+	char *driver_override, *old = dev->driver_override, *cp;
 
 	/* We need to keep extra room for a newline */
 	if (count >= (PAGE_SIZE - 1))
@@ -99,15 +95,12 @@ static ssize_t driver_override_store(struct device *_dev,
 	if (cp)
 		*cp = '\0';
 
-	device_lock(_dev);
-	old = dev->driver_override;
 	if (strlen(driver_override)) {
 		dev->driver_override = driver_override;
 	} else {
 	       kfree(driver_override);
 	       dev->driver_override = NULL;
 	}
-	device_unlock(_dev);
 
 	kfree(old);