drm/panel: panel-innolux: set display off in innolux_panel_unprepare

Move mipi_dsi_dcs_set_display_off() from innolux_panel_disable()
to innolux_panel_unprepare(), so they are consistent with
innolux_panel_enable() and innolux_panel_prepare().

This also fixes some mode check and irq timeout issue in MTK dsi code.

Since some dsi code (e.g. mtk_dsi) have following call trace:
1. drm_panel_disable(), which calls innolux_panel_disable()
2. switch to cmd mode
3. drm_panel_unprepare(), which calls innolux_panel_unprepare()

However, mtk_dsi needs to be in cmd mode to be able to send commands
(e.g. mipi_dsi_dcs_set_display_off() and mipi_dsi_dcs_enter_sleep_mode()),
so we need these functions to be called after the switch to cmd mode happens,
i.e. in innolux_panel_unprepare.

Signed-off-by: Hsin-Yi, Wang <hsinyi@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190109065922.231753-1-hsinyi@chromium.org