From: Feng Jiang <jiangfeng@xxxxxxxxxx>
When calling scnprintf() to append recovery method to event_string,
the second argument should be `sizeof(event_string) - len`, otherwise
there is a potential overflow problem.
Fixes: b7cf9f4ac1b8 ("drm: Introduce device wedged event")
Signed-off-by: Feng Jiang <jiangfeng@xxxxxxxxxx>