vulkan: make sure vk_image::format is never UNDEFINED

vk_image::android_external_format is only used for sanity check and is
removed.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22619>

src/vulkan/runtime/vk_image.c

@@ -108,9 +108,7 @@ vk_image_init(struct vk_device *device,
       assert(image->format == VK_FORMAT_UNDEFINED);
       assert(image->external_handle_types &
              VK_EXTERNAL_MEMORY_HANDLE_TYPE_ANDROID_HARDWARE_BUFFER_BIT_ANDROID);
-      image->android_external_format = ext_format->externalFormat;
-   } else {
-      image->android_external_format = 0;
+      vk_image_set_format(image, (VkFormat)ext_format->externalFormat);
    }
 #endif
 }

src/vulkan/runtime/vk_image.h

@@ -36,7 +36,13 @@ struct vk_image {
 
    VkImageCreateFlags create_flags;
    VkImageType image_type;
+
+   /* format is from VkImageCreateInfo::format or
+    * VkExternalFormatANDROID::externalFormat.  This works because only one of
+    * them can be defined and the runtime uses VkFormat for external formats.
+    */
    VkFormat format;
+
    VkExtent3D extent;
    uint32_t mip_levels;
    uint32_t array_layers;
@@ -76,9 +82,6 @@ struct vk_image {
     * but it may be overridden by the driver as needed.
     */
    unsigned ahardware_buffer_format;
-
-   /* VK_ANDROID_external_memory_android_hardware_buffer */
-   uint64_t android_external_format;
 #endif
 };
 VK_DEFINE_NONDISP_HANDLE_CASTS(vk_image, base, VkImage,