PM / QoS: return -EINVAL for bogus strings

PM / QoS: return -EINVAL for bogus strings

commit 2ca30331c156ca9e97643ad05dd8930b8fe78b01 upstream.

In the current code, if the user accidentally writes a bogus command to
this sysfs file, then we set the latency tolerance to an uninitialized
variable.

Fixes: 2d984ad132a8 (PM / QoS: Introcuce latency tolerance device PM QoS type)
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>