vulkan: Make sure we've loaded our connectors when querying plane props.

vulkan: Make sure we've loaded our connectors when querying plane props.

If you hadn't already called wsi_GetPhysicalDeviceDisplayProperties2KHR or
wsi_GetDrmDisplayEXT before calling
GetPhysicalDeviceDisplayPlaneProperties2KHR, then the connectors list
wouldn't be populated and you'd get no plane properties.  Fixes failure of
dEQP-VK.wsi.display.get_display_plane_capabilities when run on its own.

Fixes: #4575
Cc: mesa-stable
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15353>