msm: dsi-pll: update pll ref config before start for msm8996

Reset pll_verf_cfg1 to default value of 0x10 before pll
start for msm8996 based on hardware recommendation.

Change-Id: I95a89c18de4f7eb65a8ea0a8e4810560ddb0b44f
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>