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
3152 1096 8 4256 10a0 processor_thermal_device.o
File size After adding 'const':
text data bss dec hex filename
3216 1032 8 4256 10a0 processor_thermal_device.o