drm/i915: clean up inconsistent indenting

There is a statement that is indented one character too deeply,
clean this up.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210902215737.55570-1-colin.king@canonical.com