platform/x86: tc1100-wmi: Constify static attribute_group struct

The only use of tc1100_attribute_group is to pass its address to
sysfs_create_group() and sysfs_remove_group(), both which takes pointer
to const attribute_group structs. Make it const to allow the compiler to
put it in read-only memory.

Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Link: https://lore.kernel.org/r/20210605203807.60547-4-rikard.falkeborn@gmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>