powerpc/cacheinfo: Add per cpu per index shared_cpu_list

Unlike drivers/base/cacheinfo, powerpc cacheinfo code is not exposing
shared_cpu_list under /sys/devices/system/cpu/cpu<n>/cache/index<m>

Add shared_cpu_list to per cpu per index directory to maintain parity
with x86. Some scripts (example: mmtests
https://github.com/gormanm/mmtests) seem to be looking for
shared_cpu_list instead of shared_cpu_map.

Before this patch:
  # ls /sys/devices/system/cpu0/cache/index1
  coherency_line_size  number_of_sets  size  ways_of_associativity
  level                shared_cpu_map  type
  # cat /sys/devices/system/cpu0/cache/index1/shared_cpu_map
  00ff
  #

After this patch:
  # ls /sys/devices/system/cpu0/cache/index1
  coherency_line_size  number_of_sets   shared_cpu_map  type
  level                shared_cpu_list  size            ways_of_associativity
  # cat /sys/devices/system/cpu0/cache/index1/shared_cpu_map
  00ff
  # cat /sys/devices/system/cpu0/cache/index1/shared_cpu_list
  0-7
  #
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200629103703.4538-4-srikar@linux.vnet.ibm.com

arch/powerpc/kernel/cacheinfo.c

@@ -670,12 +670,20 @@ show_shared_cpumap(struct kobject *k, struct kobj_attribute *attr, char *buf, bo
 
 static ssize_t shared_cpu_map_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
 {
-	return show_shared_cpumap(k, attr, buf, false)
+	return show_shared_cpumap(k, attr, buf, false);
+}
+
+static ssize_t shared_cpu_list_show(struct kobject *k, struct kobj_attribute *attr, char *buf)
+{
+	return show_shared_cpumap(k, attr, buf, true);
 }
 
 static struct kobj_attribute cache_shared_cpu_map_attr =
 	__ATTR(shared_cpu_map, 0444, shared_cpu_map_show, NULL);
 
+static struct kobj_attribute cache_shared_cpu_list_attr =
+	__ATTR(shared_cpu_list, 0444, shared_cpu_list_show, NULL);
+
 /* Attributes which should always be created -- the kobject/sysfs core
  * does this automatically via kobj_type->default_attrs.  This is the
  * minimum data required to uniquely identify a cache.
@@ -684,6 +692,7 @@ static struct attribute *cache_index_default_attrs[] = {
 	&cache_type_attr.attr,
 	&cache_level_attr.attr,
 	&cache_shared_cpu_map_attr.attr,
+	&cache_shared_cpu_list_attr.attr,
 	NULL,
 };