drm/i915: don't block resume on fb console resume v2

The console lock can be contended, so rather than prevent other drivers
after us from being held up, queue the console suspend into the global
work queue that can happen anytime.  I've measured this to take around
200ms on my T420.  Combined with the ring freq/turbo change, we should
save almost 1/2 a second on resume.

v2: use console_trylock() to try to resume the console immediately (Chris)

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
[danvet: move dev_priv->console_resume_work next to the fbdev
pointer.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>