Input: reject inhibit and uninhibit requests on unregistering devices

When an input device is being unregistered via input_unregister_device(),
input_disconnect_device() sets dev->going_away = true under dev->mutex
and releases the mutex.

If a concurrent sysfs write to the inhibited attribute executes
input_inhibit_device() or input_uninhibit_device(), it acquires
dev->mutex. Because neither function checks dev->going_away (unlike
input_open_device()), input_uninhibit_device() proceeds to call
dev->open() and start polling on a device that is in the middle of being
unregistered and torn down.

Fix this by checking dev->going_away in input_inhibit_device() and
input_uninhibit_device() under dev->mutex and returning -ENODEV if the
device is going away.

Fixes: a181616487db ("Input: Add "inhibited" property")
Reported-by: sashiko-bot@kernel.org
Assisted-by: Antigravity:gemini-3.6-flash
Link: https://patch.msgid.link/anEolqA35rGei9ql@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>