char: xillybus: Use to_delayed_work()

Use to_delayed_work() instead of open-coding it.

Signed-off-by: Chen Ni <nichen@iscas.ac.cn>
Acked-by: Eli Billauer <eli.billauer@gmail.com>
Link: https://lore.kernel.org/r/20250414074559.3954142-1-nichen@iscas.ac.cn


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>