Input: appletouch - initialize work before device registration

Syzbot has reported warning in __flush_work(). This warning is caused by
work->func == NULL, which means missing work initialization.

This may happen, since input_dev->close() calls
cancel_work_sync(&dev->work), but dev->work initalization happens _after_
input_register_device() call.

So this patch moves dev->work initialization before registering input
device

Fixes: 5a6eb676

 ("Input: appletouch - improve powersaving for Geyser3 devices")
Reported-and-tested-by:  <syzbot+b88c5eae27386b252bbd@syzkaller.appspotmail.com>
Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
Link: https://lore.kernel.org/r/20211230141151.17300-1-paskripkin@gmail.com


Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>