media: ti-vpe: cal: Group all DMA queue fields in struct cal_dmaqueue

The cal_dmaqueue structure only contains the list of queued buffers.
Move the other fields that are logically related to the DMA queue
(current and next buffer points, state, wait queue and lock) from
cal_ctx to cal_dmaqueue.

Take this as an opportunity to document the fields usage and to give
them more appropriate names. The 'active' field stored the list of all
queued buffers, not the active buffers, so rename it to 'queue'. The
'cur_frm' and 'next_frm' are respectively renamed to 'active' and
'pending' to better explain their purpose. The 'dma_state' and
'dma_wait' fields are stripped of their 'dma_' prefix as they're now
part of cal_dmaqueue. Finally, 'slock' is renamed to 'lock'.

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>