drm/msm/dp: fix for mvid/nvid zero on sm6150 dp mst

The mvid and nvid values for the second DP mst display on
sm6150 are zero, causing display blankout. These changes
will program the mvid and nvid values for the second
display in the correct registers.

Change-Id: Ide044c89b21f686c010d612feaa8abfa537e279a
Signed-off-by: Sankeerth Billakanti <sbillaka@codeaurora.org>