drm/msm: enumerate DSI interfaces

Follow the DP example and define MSM_DSI_CONTROLLER_n enumeration.

Reviewed-by: Abhinav Kumar <[e-mail]>
Reviewed-by: Marijn Suijten <[e-mail]>
Tested-by: Marijn Suijten <[e-mail]>
Signed-off-by: Dmitry Baryshkov <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/545351/
Link: https://lore.kernel.org/r/[e-mail]

drivers/gpu/drm/msm/msm_drv.h

···
 	MSM_DP_CONTROLLER_COUNT,
 };
 
+enum msm_dsi_controller {
+	MSM_DSI_CONTROLLER_0,
+	MSM_DSI_CONTROLLER_1,
+	MSM_DSI_CONTROLLER_COUNT,
+};
+
 #define MSM_GPU_MAX_RINGS 4
 #define MAX_H_TILES_PER_DISPLAY 2
 
···
 	struct hdmi *hdmi;
 
 	/* DSI is shared by mdp4 and mdp5 */
-	struct msm_dsi *dsi[2];
+	struct msm_dsi *dsi[MSM_DSI_CONTROLLER_COUNT];
 
 	struct msm_dp *dp[MSM_DP_CONTROLLER_COUNT];