msm: mdss: Pass shift instead of bit field to hist_disable

pp_hist_disable will always use the same bit field for differing histogram
locations, just with different shift values. Store the base bit field in
pp_hist_disable.

Change-Id: I86a2f9014f0eb5cdc82a3b5998948f3a11cdff87
Signed-off-by: Carl Vanderlip <carlv@codeaurora.org>