drm/msm/dpu: drop VBIF indices

We do not expect to have other VBIFs. Drop VBIF_n indices and always use
VBIF_RT and VBIF_NRT.

Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/489571/
Link: https://lore.kernel.org/r/20220615125703.24647-3-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>