drm/i915: tune down the fast link training vs boot fail

drm/i915: tune down the fast link training vs boot fail

It's been unfixed since a while and no one is immediately working on
this. And we have the FIXME already. And now also a task in the DP
team's backlog.

Cc: Linus Torvalds <[email protected]>
Cc: [email protected]
Cc: Ville Syrjälä <[email protected]>
References: https://lists.freedesktop.org/archives/intel-gfx/2016-July/101951.html
Acked-by: Ville Syrjälä <[email protected]>
[danvet: Adjust comment per Ville's feedback.]
Signed-off-by: Daniel Vetter <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit 2dd85aeb5bc99e3763dd192cdb95ff405a102c8a)
Signed-off-by: Jani Nikula <[email protected]>