msm: mdss: Correct erroneous failure when programming LUTs

When Hist LUT and GC LUT both are enabled, the gains are
combined. The call to update the lut post combining gains
was failing as error was returned even when combining gains
was successful. Correcting the conditional check for the
same.

Change-Id: I49f657838aab1980bfe84bf4fb1e0e2e608fb2cb
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>