media: ti-vpe: cal: Remove DMA queue empty check at start streaming time

The vb2 queue ensures that the start streaming operation will only be
called with a minimal number of buffers queued to the driver. There's
thus no need to manually check if the DMA queue is empty. Remove the
check.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Benoit Parrot <bparrot@ti.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>