ACPI: make device_attribute const

Make these const as they are only passed as an argument to the function
device_create_file and device_remove_file and the corresponding
arguments are of type const.
Done using Coccinelle

Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>