drm/msm/dsi: Use one connector for dual DSI mode

Current DSI driver uses two connectors for dual DSI case even
though we only have one panel. Fix this by implementing one
connector/bridge for dual DSI use case. Use master DSI
controllers to register one connector/bridge.

Changes in v3:
- None

Reviewed-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>
[seanpaul removed unused local var causing a build warning]
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/dsi/dsi.h

@@ -100,6 +100,7 @@ bool msm_dsi_manager_cmd_xfer_trigger(int id, u32 dma_base, u32 len);
 void msm_dsi_manager_attach_dsi_device(int id, u32 device_flags);
 int msm_dsi_manager_register(struct msm_dsi *msm_dsi);
 void msm_dsi_manager_unregister(struct msm_dsi *msm_dsi);
+bool msm_dsi_manager_validate_current_config(u8 id);
 
 /* msm dsi */
 static inline bool msm_dsi_device_connected(struct msm_dsi *msm_dsi)