drm/i915: Fix includes and local vars order

Removed duplicate include and fixed comment > 80 chars.

v2: Added newline after system include and between functions

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200522131843.20477-1-stanislav.lisovskiy@intel.com