modesetting: Enable framebuffer modifiers for non-atomic
Currently the modesetting driver requires atomic modesetting support in order to enable framebuffer modifiers. However, as of Linux v5.4, the kernel refuses to let X use atomic modesetting because it does not have a complete and proper implementation. However, framebuffer modifiers do not really require atomic modesetting and will work fine with legacy KMS. The one prerequisite that the code currently has is universal planes. Atomic modesetting implies universal planes, but universal planes can also be activated separately. Enable the universal planes client capability to ensure the IN_FORMATS property of primary planes can be parsed and used to determine which format modifiers to use during framebuffer allocation. Signed-off-by: Thierry Reding <treding@nvidia.com>