PM / QoS: Export dev_pm_qos_update_user_latency_tolerance

BugLink: https://bugs.launchpad.net/bugs/1666401

nvme wants a module parameter that overrides the default latency
tolerance.  This makes it easy for nvme to reflect that default in
sysfs.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 034e7906)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-by: Tim Gardner <tim.gardner@canonical.com>
Acked-by: Colin King <colin.king@canonical.com>
Signed-off-by: Brad Figg <brad.figg@canonical.com>

drivers/base/power/qos.c

@@ -883,6 +883,7 @@ int dev_pm_qos_update_user_latency_tolerance(struct device *dev, s32 val)
 	mutex_unlock(&dev_pm_qos_mtx);
 	return ret;
 }
+EXPORT_SYMBOL_GPL(dev_pm_qos_update_user_latency_tolerance);
 
 /**
  * dev_pm_qos_expose_latency_tolerance - Expose latency tolerance to userspace