msm: mdss: Fix slower clocks during histogram and hist LUT accesses

Slower CNOC clock rates cause histogram and hist LUT access to take
longer time. Fix CNOC clock configuration at optimum rate in order
to avoid slow accesses to histogram and hist LUT.

Change-Id: I066bae9fd0b4261b71248cffea65d8949ff6aae2
Signed-off-by: Ping Li <quicpingli@codeaurora.org>