drm/panel: boe-tv101wum-nl6: make use of prepare_prev_first

drm/panel: boe-tv101wum-nl6: make use of prepare_prev_first

The panel on sc7180-trogdor-wormdingler and
sc7180-trogdor-quackingstick hasn't been coming up since commit
9e15123eca79 ("drm/msm/dsi: Stop unconditionally powering up DSI hosts
at modeset"). Let's add "prepare_prev_first" as has been done for many
other DSI panels.

Fixes: 9e15123eca79 ("drm/msm/dsi: Stop unconditionally powering up DSI hosts at modeset")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Link: https://lore.kernel.org/r/20240216123111.1.I71c103720909790e1ec5a3f5bd96b18ab7b596fa@changeid
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240216123111.1.I71c103720909790e1ec5a3f5bd96b18ab7b596fa@changeid