drm/msm/dpu: set dirty_fb flag while in self refresh mode

drm/msm/dpu: set dirty_fb flag while in self refresh mode

While in virtual terminal mode with PSR enabled, there will be
no atomic commits triggered without dirty_fb being set. This
will create a notion of no screen update. Allow atomic commit
when dirty_fb ioctl is issued, so that it can trigger a PSR exit
and shows update on the screen.

Reported-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/all/20230326162723.3lo6pnsfdwzsvbhj@ripper/
Signed-off-by: Vinod Polimera <quic_vpolimer@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/530206/
Link: https://lore.kernel.org/r/1680271114-1534-2-git-send-email-quic_vpolimer@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>