msm: mdss: Reset the col_en flag after disabling the Hist Intr

Race condition occured between Hist Disable and Hist ISR
function becasue of below change ID, hence make sure that the
'col_en' is set to false only after hist isr is disabled.
change ID: Ib24251a00903d9f3f20034be3d12fb1e321b4aba

Change-Id: I0600b9b0c3435c6ed749f7753b9b8defd31d994a
Signed-off-by: Raghavendra Ambadas <rambad@codeaurora.org>