drm/rockchip: dw-mipi-dsi: defer probe if panel is not loaded

This ensures that the output resolution is known before fbcon loads.
mipi_dsi_host_register() is moved above dw_mipi_dsi_register() to
simplify error cleanup since the order of these operations does not
matter.

Signed-off-by: John Keeping <john@metanate.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/20170224125506.21533-22-john@metanate.com