drm/msm/dpu: Start frame done timer after encoder kickoff

Starting the frame done timer before the encoder is finished kicking off
can lead to unnecessary frame done timeouts when the device is
experiencing heavy load (ex. when debug logs are enabled).

Thus, create a separate API for starting the encoder frame done timer and
call it after the encoder kickoff is finished

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/637502/
Link: https://lore.kernel.org/r/20250214-concurrent-wb-v6-11-a44c293cf422@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>