msm: mdss: Fix bugs in mdss code

This patch fixes bugs in mdss code, including uninitialized variables,
potential integer overflow, unnecessary condition check, incorrect use
of logical and bitwise operator and unreleased memory in error case.

Change-Id: Id579edc5e8f78aa8c295f1fccc88230ca00202ad
Signed-off-by: Ping Li <pingli@codeaurora.org>