vulkan: add size tracking to buffer structs

libavutil/vulkan.c

@@ -295,6 +295,8 @@ int ff_vk_create_buf(FFVulkanContext *s, FFVkBuffer *buf, size_t size,
         return AVERROR_EXTERNAL;
     }
 
+    buf->size = size;
+
     return 0;
 }
 

libavutil/vulkan.h

@@ -94,6 +94,7 @@ typedef struct FFVkBuffer {
     VkBuffer buf;
     VkDeviceMemory mem;
     VkMemoryPropertyFlagBits flags;
+    size_t size;
 } FFVkBuffer;
 
 typedef struct FFVkQueueFamilyCtx {