PM QoS: Fix kzalloc() parameters swapped in pm_qos_power_open()

sparse spotted that the kzalloc() in pm_qos_power_open() in the
current Linus' git tree had its parameters swapped.  Fix this.

Signed-off-by: David Alan Gilbert <linux@treblig.org>
Acked-by: mark gross <markgross@thegnar.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>