drm/panel: jh057n00900: Move mipi_dsi_dcs_set_display_off to disable()

This makes it symmetric with the panel init happening in enable().

Signed-off-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/e2c31d34ce1f917065d590297e5115a4ca954874.1564146727.git.agx@sigxcpu.org