vulkan/wsi: disable the hardware cursor

Ensure the hardware cursor is disabled when we set the mode for a
VkDisplayKHR object. The extension doesn't expose any mechanisms to
program the hardware cursor, so we need to ensure it is hidden.

Currently, it seems like X is responsible for disabling the cursor
before handing over the lease. But that seems a little frail, and we
should be disabling the cursor ourselves so it works correctly
independently of how the lease was prepared for us.

Signed-off-by: Andres Rodriguez <andresx7@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Tested-by: Marge Bot <mesa/mesa!1922>
Part-of: <mesa/mesa!1922>