Input: byd - synchronize timer deletion before freeing private data

Input: byd - synchronize timer deletion before freeing private data

byd_disconnect() uses timer_delete() before freeing the driver's private
data.  This does not wait for a running byd_clear_touch() callback, which
dereferences the private data and its psmouse pointer.  A callback racing
with disconnect can therefore access the private data after it has been
freed.  The timer can also still be re-armed by byd_process_byte() while
the disconnect is in progress.

Use timer_shutdown_sync() before freeing the private data: it waits for
a running callback and turns any later re-arm attempt into a no-op.

Fixes: 2d5f5611dd0d ("Input: byd - enable absolute mode")
Cc: stable@vger.kernel.org
Signed-off-by: Linmao Li <lilinmao@kylinos.cn>
Link: https://patch.msgid.link/20260720061259.1601281-1-lilinmao@kylinos.cn
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>