media: rkisp1: cap: initialize dma buf address in 'buf_init' cb

Initializing the dma addresses of the capture buffers can
move to the 'buf_init' callback, since it is enough to do
it once for each buffer and not every time it is queued.

Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>