drm/fourcc: add AMD_FMT_MOD_TILE_GFX9_4K_D_X

This is used when radeonsi export small texture's modifier
to user with eglExportDMABUFImageQueryMESA().

mesa changes is available here:
mesa/mesa!31658



Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Qiang Yu <qiang.yu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>