vulkan/wsi/wayland: Remove roundtrip when creating image

There's no need to call wl_display_roundtrip() after trying to create a
buffer through wl_drm; if it succeeds then everything is fine, and if it
fails, then we get a fatal protocol error so can't recover anyway.

Additionally, doing a roundtrip on the default / main application queue,
is destructive anyway, so would need to be its own queue.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: mesa-stable@lists.freedesktop.org