vulkan/wsi: Store the instance allocator in wsi_device

vulkan/wsi: Store the instance allocator in wsi_device

We already have wsi_device and we know the instance allocator at
wsi_device_init time so there's no need to pass it into the physical
device queries.  This also fixes a memory allocation domain bug that can
occur if CreateSwapchain gets called prior to any queries (not likely)
in which case the cached connection gets allocated off the device
instead of the instance.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>