HID: input: call input_sync() when automatically releasing a key

We need to emit EV_SYN/SYN_REPORT between key press and release, otherwise
userspace is allowed to "swallow" the event.

[jkosina@suse.com: Dmitry says that he's observing this behavior with
 Plantronics headset]

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>