drm/msm/dpu: make "vblank timeout" more useful

We have several reports of vblank timeout messages. However after some
debugging it was found that there might be different causes to that.
To allow us to identify the DPU block that gets stuck, include the
actual CTL_FLUSH value into the timeout message.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/579849/
Link: https://lore.kernel.org/r/20240226-fd-dpu-debug-timeout-v4-1-51eec83dde23@linaro.org