drm/exynos: g2d: remove runqueue nodes in g2d_{close,remove}()

The driver might be closed (and/or removed) while there are still
nodes queued for processing.
Make sure to remove these nodes, which means all of them in
the case of g2d_remove() and only those belonging to the
corresponding process in g2d_close().

Signed-off-by: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>