drm/exynos/dsi: Remove error handling for bridge_node DT parsing

Remove the error handling of bridge_node because the bridge_node is
optional.

For example, In case of Exynos SoC, a bridge device such as mDNIe and
MIC could be placed between Display Controller and MIPI DSI device but
the bridge device is optional.

Signed-off-by: Hoegeun Kwon <hoegeun.kwon@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>