RDMA/core: Constify struct attribute_group

The only usage of the pma_table field in the ib_port struct is to pass its
address to sysfs_create_group() and sysfs_remove_group(). Make it const to
make it possible to constify a couple of static struct
attribute_group. This allows the compiler to put them in read-only memory.

Link: https://lore.kernel.org/r/20200930224004.24279-2-rikard.falkeborn@gmail.comSigned-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/core/sysfs.c

@@ -59,7 +59,7 @@ struct ib_port {
 	struct gid_attr_group *gid_attr_group;
 	struct attribute_group gid_group;
 	struct attribute_group *pkey_group;
-	struct attribute_group *pma_table;
+	const struct attribute_group *pma_table;
 	struct attribute_group *hw_stats_ag;
 	struct rdma_hw_stats   *hw_stats;
 	u8                     port_num;
@@ -653,17 +653,17 @@ static struct attribute *pma_attrs_noietf[] = {
 	NULL
 };
 
-static struct attribute_group pma_group = {
+static const struct attribute_group pma_group = {
 	.name  = "counters",
 	.attrs  = pma_attrs
 };
 
-static struct attribute_group pma_group_ext = {
+static const struct attribute_group pma_group_ext = {
 	.name  = "counters",
 	.attrs  = pma_attrs_ext
 };
 
-static struct attribute_group pma_group_noietf = {
+static const struct attribute_group pma_group_noietf = {
 	.name  = "counters",
 	.attrs  = pma_attrs_noietf
 };
@@ -778,7 +778,7 @@ alloc_group_attrs(ssize_t (*show)(struct ib_port *,
  * Figure out which counter table to use depending on
  * the device capabilities.
  */
-static struct attribute_group *get_counter_table(struct ib_device *dev,
+static const struct attribute_group *get_counter_table(struct ib_device *dev,
 						       int port_num)
 {
 	struct ib_class_port_info cpi;