drm/msm/dpu: reserve CDM blocks for DP if mode is YUV420

Reserve CDM blocks for DP if the mode format is YUV420. Currently this
reservation only works for writeback and DP if the format is YUV420. But
this can be easily extented to other YUV formats for DP.

Changes in v2:
	- Minor code simplification

Signed-off-by: Paloma Arellano <quic_parellan@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/579630/
Link: https://lore.kernel.org/r/20240222194025.25329-19-quic_parellan@quicinc.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>