linux-phytec-ti

drm/exynos: Remove PTN3460 dependency

Now that the PTN3460 driver has been rewritten as a proper I2C driver
and there is infrastructure to hook up the bridge with a DRM device, it
is no longer necessary to have this dependency to ensure the correct
build mode.

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