drm/arm: Fix spelling typo in comments

Fix spelling typo in comments.

Reported-by: k2ci <kernel-bot@kylinos.cn>
Signed-off-by: pengfuyuan <pengfuyuan@kylinos.cn>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220426121639.39160-1-pengfuyuan@kylinos.cn