If mipi_dsi_dcs_set_display_on() returned an error then we'd store
that in the "ret" variable and jump to error handling. We'd then
attempt an orderly poweroff. Unfortunately we then blew away the value
stored in "ret". That means that if the orderly poweroff actually
worked then we're return 0 (no error) from hx8394_enable() even though
the panel wasn't enabled.

Fix this by not blowing away "ret".

Found by code inspection.

Fixes: 65dc9360 ("drm: panel: Add Himax HX8394 panel controller driver")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20240517143643.1.I0a6836fffd8d7620f353becb3df2370d2898f803@changeidSigned-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240517143643.1.I0a6836fffd8d7620f353becb3df2370d2898f803@changeid