drm/tegra: dsi: Use proper back-porch for non-sync video mode
drm/tegra: dsi: Use proper back-porch for non-sync video mode

In video modes without sync pulses, the horizontal back-porch needs to
include the horizontal sync width.

Signed-off-by: Thierry Reding <3055038c414aef68bf32c33b8118623e7554e0f2@nvidia.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs