drm/dp: add an API to indicate if sink supports VSC SDP

YUV420 format is supported only in the VSC SDP packet and not through
MSA. Hence add an API which indicates the sink support which can be used
by the rest of the DP programming.

changes in v5:
	- rebased on top of drm-tip

changes in v4:
	- bail out early if dpcd rev check fails

changes in v3:
	- fix the commit title prefix to drm/dp
	- get rid of redundant !!
	- break out this change from series [1] to get acks from drm core
	  maintainers

Changes in v2:
	- Move VSC SDP support check API from dp_panel.c to
	  drm_dp_helper.c

[1]: https://patchwork.freedesktop.org/series/129180/



Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Paloma Arellano <quic_parellan@quicinc.com>
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240215191556.3227259-1-quic_abhinavk@quicinc.com