media: iris: Add support for drain sequence in encoder video device

media: iris: Add support for drain sequence in encoder video device

Add support for handling start and stop commands, including the
end-of-stream (drain) sequence, in the encoder video device.

This enables proper signaling to the firmware and ensures that all
pending frames are processed and flushed before completing the stream.

Tested-by: Vikash Garodia <quic_vgarodia@quicinc.com> # X1E80100
Reviewed-by: Vikash Garodia <quic_vgarodia@quicinc.com>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8550-HDK
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8650-HDK
Signed-off-by: Dikshita Agarwal <quic_dikshita@quicinc.com>
Tested-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org> # x1e80100-crd
Signed-off-by: Bryan O'Donoghue <bod@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>