vulkan/wsi/display: don't report support if there is no drm fd
This partially deals with #4688
Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Cc: mesa-stable
This partially deals with #4688
Signed-off-by: Lionel Landwerlin lionel.g.landwerlin@intel.com Cc: mesa-stable