nvk: Advertise ICD/loader interface version 4

We can't advertise v5 yet because we don't support Vulkan 1.1 yet.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24326>

src/nouveau/vulkan/nvk_instance.c

@@ -9,6 +9,59 @@ nvk_EnumerateInstanceVersion(uint32_t *pApiVersion)
    return VK_SUCCESS;
 }
 
+/* vk_icd.h does not declare this function, so we declare it here to
+ * suppress Wmissing-prototypes.
+ */
+PUBLIC VKAPI_ATTR VkResult VKAPI_CALL
+vk_icdNegotiateLoaderICDInterfaceVersion(uint32_t* pSupportedVersion);
+
+PUBLIC VKAPI_ATTR VkResult VKAPI_CALL
+vk_icdNegotiateLoaderICDInterfaceVersion(uint32_t* pSupportedVersion)
+{
+   /* For the full details on loader interface versioning, see
+    * <https://github.com/KhronosGroup/Vulkan-LoaderAndValidationLayers/blob/master/loader/LoaderAndLayerInterface.md>.
+    * What follows is a condensed summary, to help you navigate the large and
+    * confusing official doc.
+    *
+    *   - Loader interface v0 is incompatible with later versions. We don't
+    *     support it.
+    *
+    *   - In loader interface v1:
+    *       - The first ICD entrypoint called by the loader is
+    *         vk_icdGetInstanceProcAddr(). The ICD must statically expose this
+    *         entrypoint.
+    *       - The ICD must statically expose no other Vulkan symbol unless it is
+    *         linked with -Bsymbolic.
+    *       - Each dispatchable Vulkan handle created by the ICD must be
+    *         a pointer to a struct whose first member is VK_LOADER_DATA. The
+    *         ICD must initialize VK_LOADER_DATA.loadMagic to ICD_LOADER_MAGIC.
+    *       - The loader implements vkCreate{PLATFORM}SurfaceKHR() and
+    *         vkDestroySurfaceKHR(). The ICD must be capable of working with
+    *         such loader-managed surfaces.
+    *
+    *    - Loader interface v2 differs from v1 in:
+    *       - The first ICD entrypoint called by the loader is
+    *         vk_icdNegotiateLoaderICDInterfaceVersion(). The ICD must
+    *         statically expose this entrypoint.
+    *
+    *    - Loader interface v3 differs from v2 in:
+    *        - The ICD must implement vkCreate{PLATFORM}SurfaceKHR(),
+    *          vkDestroySurfaceKHR(), and other API which uses VKSurfaceKHR,
+    *          because the loader no longer does so.
+    *
+    *    - Loader interface v4 differs from v3 in:
+    *        - The ICD must implement vk_icdGetPhysicalDeviceProcAddr().
+    *
+    *    - Loader interface v5 differs from v4 in:
+    *        - The ICD must support Vulkan API version 1.1 and must not return
+    *          VK_ERROR_INCOMPATIBLE_DRIVER from vkCreateInstance() unless a
+    *          Vulkan Loader with interface v4 or smaller is being used and the
+    *          application provides an API version that is greater than 1.0.
+    */
+   *pSupportedVersion = MIN2(*pSupportedVersion, 4u);
+   return VK_SUCCESS;
+}
+
 static const struct vk_instance_extension_table instance_extensions = {
 #ifdef NVK_USE_WSI_PLATFORM
    .KHR_get_surface_capabilities2 = true,