drm/msm/dpu: Set input_sel bit for INTF

Set the input_sel bit for encoders as it was missed in the initial
implementation.

Reported-by: Rob Clark <robdclark@gmail.com>
Closes: https://gitlab.freedesktop.org/drm/msm/-/issues/39
Fixes: 91143873

 ("drm/msm/dpu: Add MISR register support for interface")
Signed-off-by: Jessica Zhang <quic_jesszhan@quicinc.com>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/572007/
Link: https://lore.kernel.org/r/20231213-encoder-fixup-v4-1-6da6cd1bf118@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>