drm/msm/dpu: try reserving the DSPP-less LM first

drm/msm/dpu: try reserving the DSPP-less LM first

On most of the platforms only some mixers have connected DSPP blocks.
If DSPP is not required for the CRTC, try looking for the LM with no
DSSP block, leaving DSPP-enabled LMs to CRTCs which actually require
those.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/698773/
Link: https://lore.kernel.org/r/20260115-dpu-fix-dspp-v1-2-b73152c147b3@oss.qualcomm.com