media: ti-vpe: cal: fix queuing of the initial buffer

When starting streaming the driver currently programs the buffer
address to the CAL base-address register and assigns the buffer pointer
to ctx->dma.pending. This is not correct, as the buffer is not
"pending", but active, and causes the first buffer to be needlessly
written twice.

Fix this by assigning the buffer pointer to ctx->dma.active.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>