drm/msm/dp: fix programming of DP_MISC1_MISC0 register

As part of DP ON sequence to send pixel data, the DP_MISC1_MISC0
register needs to be programmed with colorimetry data based on the
calculated values for the given DP connection cycle. Avoid reading
the existing stale values in the register and appending the new
values to it.

Change-Id: I8eb2c75c06618fd549242affa7aa9f4a91f4b76e
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>