drivers base/arch_topology: Remove 'struct sched_domain' forward declaration

The sched domain pointer argument from topology_get_freq_scale() and
topology_get_cpu_scale() got removed by commit 7673c8a4
("sched/cpufreq: Remove arch_scale_freq_capacity()'s 'sd' parameter")
and commit 8ec59c0f ("sched/topology: Remove unused 'sd' parameter
from arch_scale_cpu_capacity()").

So the 'struct sched_domain' forward declaration is no longer needed.
Remove it.
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
Link: https://lore.kernel.org/r/20200211181515.32570-2-dietmar.eggemann@arm.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/arch_topology.h

@@ -16,7 +16,6 @@ bool topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu);
 
 DECLARE_PER_CPU(unsigned long, cpu_scale);
 
-struct sched_domain;
 static inline
 unsigned long topology_get_cpu_scale(int cpu)
 {