drm/msm/dp: update is_connected status base on sink count at dp_pm_resume()

Currently at dp_pm_resume() is_connected state is decided base on hpd connection
status only. This will put is_connected in wrongly "true" state at the scenario
that dongle attached to DUT but without hmdi cable connecting to it. Fix this
problem by adding read sink count from dongle and decided is_connected state base
on both sink count and hpd connection status.

Changes in v2:
-- remove dp_get_sink_count() cand call drm_dp_read_sink_count()

Changes in v3:
-- delete status local variable from dp_pm_resume()

Changes in v4:
-- delete un necessary comment at dp_pm_resume()

Fixes: d9aa6571

 ("drm/msm/dp: check sink_count before update is_connected status")
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>
Link: https://lore.kernel.org/r/1628092261-32346-1-git-send-email-khsieh@codeaurora.org
Tested-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>