video: tegra: fb: initialize mode width and height

Ensure the modedb modes have valid panel dimensions.

Change-Id: I1467b6f67021e25d89dd3ed852c6b5b13b26854a
Signed-off-by: Michael I. Gold <gold@nvidia.com>
Reviewed-on: http://git-master/r/166373
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Dan Willemsen <dwillemsen@nvidia.com>
Reviewed-by: Jon Mayo <jmayo@nvidia.com>
Reviewed-by: Kevin Huang (Eng-SW) <kevinh@nvidia.com>