media: venus: preserve DRC state across seeks

DRC events can happen virtually at anytime, including when we are
starting a seek. Should this happen, we must make sure to return to the
DRC state, otherwise the firmware will expect buffers of the new
resolution whereas userspace will still work with the old one.

Returning to the DRC state upon resume for seeking makes sure that the
client will get the DRC event and will reallocate the buffers to fit the
firmware's expectations.

Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>