hwcontext_vulkan: use portability subset if available

libavutil/hwcontext_vulkan.c

@@ -340,11 +340,13 @@ typedef struct VulkanOptExtension {
 } VulkanOptExtension;
 
 static const VulkanOptExtension optional_instance_exts[] = {
-    /* For future use */
+    /* Pointless, here avoid zero-sized structs */
+    { VK_KHR_PORTABILITY_ENUMERATION_EXTENSION_NAME,          FF_VK_EXT_NO_FLAG                },
 };
 
 static const VulkanOptExtension optional_device_exts[] = {
     /* Misc or required by other extensions */
+    { VK_KHR_PORTABILITY_SUBSET_EXTENSION_NAME,               FF_VK_EXT_NO_FLAG                },
     { VK_KHR_PUSH_DESCRIPTOR_EXTENSION_NAME,                  FF_VK_EXT_NO_FLAG                },
     { VK_KHR_SAMPLER_YCBCR_CONVERSION_EXTENSION_NAME,         FF_VK_EXT_NO_FLAG                },