radv: Support loader interface version 3.

Port of 1e41d7f7b0855934744fe578ba4eae9209ee69f7:
"anv: Support loader interface version 3 (patch v2)"

Signed-off-by: Bas Nieuwenhuizen <basni@google.com>
Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>

src/amd/vulkan/radv_device.c

@@ -2032,3 +2032,48 @@ void radv_DestroySampler(
 		return;
 	vk_free2(&device->alloc, pAllocator, sampler);
 }
+
+
+/* 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.
+	*/
+	*pSupportedVersion = MIN2(*pSupportedVersion, 3u);
+	return VK_SUCCESS;
+}