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.
File size before:
text data bss dec hex filename
1120 544 16 1680 690 kernel/ksysfs.o
File size After adding 'const':
text data bss dec hex filename
1160 480 16 1656 678 kernel/ksysfs.o