drm/bridge: dw-mipi-dsi: Find the possible DSI devices

Finding panel_or_bridge might vary based on associated
DSI devices like DSI panel, bridge, and I2C based DSI
bridge.

1. DSI panels and bridges will invoke the host attach
   from probe in order to find the panel_or_bridge.

   chipone_probe()
       dw_mipi_dsi_host_attach().start
	   dw_mipi_dsi_panel_or_bridge()
		...found the panel_or_bridge...

   ltdc_encoder_init().start
       dw_mipi_dsi_bridge_attach().start
		   dw_mipi_dsi_host_attach().start
		       chipone_attach(). start

	               chipone_attach(). done
		   dw_mipi_dsi_host_attach().done
       dw_mipi_dsi_bridge_attach(). done
   ltdc_encoder_init().done

2. I2C based DSI bridge will invoke the drm_bridge_attach
   from bridge attach in order to find the panel_or_bridge.

   ltdc_encoder_init().start
       dw_mipi_dsi_bridge_attach().start
	   dw_mipi_dsi_panel_or_bridge()
		...found the panel_or_bridge...
		   dw_mipi_dsi_host_attach().start
		       sn65dsi83_attach(). start

	               sn65dsi83_attach(). done
		   dw_mipi_dsi_host_attach().done
       dw_mipi_dsi_bridge_attach(). done
   ltdc_encoder_init().done

So, invoke the panel_or_bridge from host attach and
bridge attach in order to find all possible DSI devices.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Yannick Fertre <yannick.fertre@foss.st.com>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210704140309.268469-1-jagan@amarulasolutions.com