vulkan/instance: Use vk_error in vk_instance_init

vulkan/instance: Use vk_error in vk_instance_init

We have to be a bit careful here.  Calling log functions during instance
initialization can be a bit sketchy.  However, we know that __vk_log_impl
only ever touches the callbacks lists if instance->base.client_visible
so it's safe to call vk_error as soon as we've set up instance_callbacks.

Tested-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13045>