drm/msm/dpu: Remove call to drm_mode_set_crtcinfo

Now that mode_fixup has been removed, we can just rely on the call
from drm_helper_probe_single_connector_modes(),

Reviewed-by: Rob Clark <robdclark@chromium.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20190617200405.131843-1-sean@poorly.run