cpufreq: armada-8k: Avoid excessive stack usage

In some build configurations (e.g. x86 allmodconfig), 2 cpu_mask
variables exceeds the max stack frame size:

drivers/cpufreq/armada-8k-cpufreq.c:203:1: error: the frame size of 2128 bytes is larger than 2048 bytes

Fix it by making "cpus" static which is fine given that module init is
only called once.

Signed-off-by: Rob Herring (Arm) <[e-mail]>
Signed-off-by: Viresh Kumar <[e-mail]>

drivers/cpufreq/armada-8k-cpufreq.c

···
 	int ret = 0, opps_index = 0, cpu, nb_cpus;
 	struct freq_table *freq_tables;
 	struct device_node *node;
-	struct cpumask cpus;
+	static struct cpumask cpus;
 
 	node = of_find_matching_node_and_match(NULL, armada_8k_cpufreq_of_match,
 					       NULL);