[media] v4l: vsp1: Simplify frame end processing

The DRM pipeline, as it runs in automatic restart mode, never sees the
pipeline state set to VSP1_PIPELINE_STOPPING or VSP1_PIPELINE_STOPPED
when running the frame end interrupt handler. We can thus skip the
checks various checks in the handler and return immediately.

Similarly the DRM frame end handler calls vsp1_pipeline_run()
unnecessarily, as the state there is never VSP1_PIPELINE_STOPPED. Remove
the function call and the frame end handler is it's now empty.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>