drm/exynos: mic: add a bridge at probe

This patch moves drm_bridge_add call into probe.

It doesn't need to call drm_bridge_add call every time
bind callback is called.

Changelog v2
- moved drm_bridge_remove call into remove callback.
- corrected description.

Suggested-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>