drm/i915: pre-fixes for checkpatch

Since I'll need to modify i915_gem_object_bind_to_gtt(), fix the errors
now to get checkpatch to not complain.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
[danvet: Resolve conflict with Chris' improved debug output, and
bikeshed the new variable with s/max/gtt_max/ a bit while at it.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>