drm/panel-edp: Fix typo in kerneldoc comment (appers=>appears)

Ever since I got the spell-check working in my editor this one has
been bugging me. Fix it.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220720162314.1.Ieef5bc3848df40b71605b70bb571d6429e8978de@changeid