chardev/char-pty: send CHR_EVENT_CLOSED on disconnect

chardev/char-pty: send CHR_EVENT_CLOSED on disconnect

Change makes code symmetric to the code, which handles
the "connected" state, i.e. send CHR_EVENT_CLOSED when
state changes from "connected" to "disconnected".

This behavior is similar to char-socket, for example.

Signed-off-by: Roman Penyaev <r.peniaev@gmail.com>
Reviewed-by: "Marc-André Lureau" <marcandre.lureau@redhat.com>
Reviewed-by: "Alex Bennée" <alex.bennee@linaro.org>
Cc: qemu-devel@nongnu.org
Message-ID: <20250123085327.965501-2-r.peniaev@gmail.com>