msm: mdss: replace mdss_fudge_factor with mult_factor

Currently there are two different data structure representing
multiplication factors. Replace internal one, mdss_fudge_factor, and
with the one shared with user-space, mult_factor.

Change-Id: I9e0dcc092b4f9033cbfcd7e185e642c922e29a27
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>