drivers/firmware/psci: Assign @err directly in hotplug_tests()

The return value of down_and_up_cpus() can be assigned to @err directly.
With that, the useless assignment to @err with zero can be dropped.
Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20200630075943.203954-1-gshan@redhat.comSigned-off-by: Will Deacon <will@kernel.org>

drivers/firmware/psci/psci_checker.c

@@ -199,13 +199,12 @@ static int hotplug_tests(void)
 	if (!page_buf)
 		goto out_free_cpu_groups;
 
-	err = 0;
 	/*
 	 * Of course the last CPU cannot be powered down and cpu_down() should
 	 * refuse doing that.
 	 */
 	pr_info("Trying to turn off and on again all CPUs\n");
-	err += down_and_up_cpus(cpu_online_mask, offlined_cpus);
+	err = down_and_up_cpus(cpu_online_mask, offlined_cpus);
 
 	/*
 	 * Take down CPUs by cpu group this time. When the last CPU is turned