chardev/char-socket: Function headers refactoring

chardev/char-socket: Function headers refactoring

Upcoming websocket support requires additional parameters in function
headers that are already overloaded. This patch replaces the bunch of
parameters with a single structure pointer.

Signed-off-by: Julia Suvorova <jusual@mail.ru>
Message-Id: <20181018223501.21683-2-jusual@mail.ru>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>