drm/panel-elida-kd35t133: hold panel in reset for unprepare

For devices like the Anbernic RG351M and RG351P the panel is wired to
an always on regulator. When the device suspends and wakes up, there
are some slight artifacts on the screen that go away over time. If
instead we hold the panel in reset status after it is unprepared,
this does not happen.

Fixes: 5b660336 ("drm/panel: add panel driver for Elida KD35T133 panels")
Signed-off-by: Chris Morgan <macromorgan@hotmail.com>
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Link: https://lore.kernel.org/r/20231117194405.1386265-3-macroalpha82@gmail.comSigned-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20231117194405.1386265-3-macroalpha82@gmail.com

drivers/gpu/drm/panel/panel-elida-kd35t133.c

@@ -104,6 +104,8 @@ static int kd35t133_unprepare(struct drm_panel *panel)
 		return ret;
 	}
 
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+
 	regulator_disable(ctx->iovcc);
 	regulator_disable(ctx->vdd);