drm/i915: fix typos in comments

Spelling mistakes (triple letters) in comments.
Detected with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220521111145.81697-90-Julia.Lawall@inria.fr