ACPI / button: Using input_set_capability() to mark device's event capability

Input layer provides input_set_capability() to set input device's event
related bits. This patch is to use it to replace origin code.

Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>