PM: QoS: Use kcalloc() instead of kzalloc()

Use 2-factor multiplication argument form kcalloc() instead
of kzalloc().

Link: https://github.com/KSPP/linux/issues/162


Signed-off-by: Erick Archer <erick.archer@gmx.com>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>