drm/omap: dmm_tiler: Remove the dma_async_issue_pending() call

dma_sync_wait() is calling it so no need to call it in the driver.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190731094233.13890-3-peter.ujfalusi@ti.com