msm: mdss: Fix warnings when using different compilers

Uninitialized variables generate warnings for gcc-4.5.2 compiler.
These variables are only initialized for video mode configuration.
Fix this issue by initializing the variables.

Change-Id: Ib51d7afae19b77d3149f3ee3e041209a552d5c82
Signed-off-by: Chandan Uddaraju <chandanu@codeaurora.org>