drm/i915: Change forcewake timeout to 2ms

A designer familiar with the hardware has stated that the forcewake
timeout can theoretically be as high as a little over 1ms. Therefore we
modify our code to use 2ms (appropriate fudge and because we don't want
to round down).

Hopefully this can't prevent spurious timeouts.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Acked-by: Chris Wilson <chris@chris-wilson.oc.uk>
[danvet: again fix conflict with vlv patch.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>