drm/msm/dpu1: don't choke on disabling the writeback connector

During suspend/resume process all connectors are explicitly disabled and
then reenabled. However resume fails because of the connector_status check:

[ 1185.831970] [dpu error]connector not connected 3

It doesn't make sense to check for the Writeback connected status (and
other drivers don't perform such check), so drop the check.

Fixes: 71174f36 ("drm/msm/dpu: move writeback's atomic_check to dpu_writeback.c")
Cc: stable@vger.kernel.org
Reported-by: Leonard Lausen <leonard@lausen.nl>
Closes: drm/msm#57


Tested-by: György Kurucz <me@kuruczgy.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>