drm/rockchip: Reorder drm bind/unbind sequence

Current drm bind/unbind sequence would cause some memory issues.
For example we should not cleanup iommu before cleanup mode config.

Reorder bind/unbind sequence, follow exynos drm.

Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
[seanpaul fixed spelling typo in commit subject]
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1491481885-13775-11-git-send-email-jeffy.chen@rock-chips.com