drm/msm/dsi: Move dsi panel init into modeset init path

Since deferred probe from the modeset init path now works, we can move
the panel initialization from detect() into connector init. This
avoids doing work in detect() and hopefully will result in a more
deterministic boot sequence between devices with a dsi panel, and those
with an external bridge.

Reviewed-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190617201301.133275-9-sean@poorly.run