drm/msm/dp: add support for HDR over MST

HDR10 implementation is missing support for multiple streams.
This patch enables programming of STREAM_1 registers in the DP
driver for supporting HDR10 playback.

CRs-fixed: 2395236
Change-Id: I123942a2d16c9d293a376ff90e19a26a338939d5
Signed-off-by: Steve Cohen <cohens@codeaurora.org>