block: constify struct part_attr_group

The struct is never modified so it can be const.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://lore.kernel.org/r/20230419-const-partition-v3-3-4e14e48be367@weissschuh.netSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/partitions/core.c

@@ -228,7 +228,7 @@ static struct attribute *part_attrs[] = {
 	NULL
 };
 
-static struct attribute_group part_attr_group = {
+static const struct attribute_group part_attr_group = {
 	.attrs = part_attrs,
 };