vt(4): Skip vt_flush() for nested panics

[dumbbell]

Summary

Why

If there is a problem with DRM drivers or in their integration with vt(4) and displaying something on the console triggers a panic, there is a high chance that displaying that panic will trigger another one, recursively.

How

If vt_flush() is called and it detects is is called resursively from another panic, it return immediately, doing nothing, to avoid the risk of triggering another panic.

[manu]

sys/dev/vt/vt_core.c

1489

Extra blank line.

3117

Is this supposed to be part of this patch ?

[dumbbell]

Address @manu comments.

[dumbbell]

sys/dev/vt/vt_core.c

1489

Removed extra blank line.

3117

Removed lines that were not supposed to be in the patch.