drm: exynos: dsi: Drop explicit call to bridge detach

Exynos DSI already converted into a bridge driver, so bridge
detach will suppose happened during bridge chain removal done
by the bridge core.

Drop the explicit call chain to detach the bridge.

Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>