drm/msm/dsi: Set msm_dsi->encoders before initializing bridge

The commit "drm: bridge: Link encoder and bridge in core code" updated
the drm_bridge_attach() API to also include the drm_encoder pointer
the bridge attaches to.

The func msm_dsi_manager_bridge_init() now relies on the drm_encoder
pointer stored in msm_dsi->encoders to pass the encoder to the bridge
API.

msm_dsi->encoders is unfortunately set after this function is called,
resulting in us passing a NULL pointer to drm_brigde_attach. This
results in an error and the DSI driver probe fails.

Move the initialization of msm_dsi->encoders[] a bit up. Also, don't
try to set the encoder's bridge. That's now managed by the bridge
API.

Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>