ACPI: BGRT: constify attribute_group structures

attribute_groups are not supposed to change at runtime. All functions
working with attribute_groups provided by <linux/sysfs.h> work with const
attribute_group. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/bgrt.c

@@ -76,7 +76,7 @@ static struct bin_attribute *bgrt_bin_attributes[] = {
 	NULL,
 };
 
-static struct attribute_group bgrt_attribute_group = {
+static const struct attribute_group bgrt_attribute_group = {
 	.attrs = bgrt_attributes,
 	.bin_attrs = bgrt_bin_attributes,
 };