lavfi/vf_libplacebo: require v5.278 for importing

Importing Vulkan device on older versions no longer works due to the
lavu vulkan API changes (specifically, the switch to planar textures by
default). Additionally, importing on versions that don't suppirt
lock/unlock_queue is unsafe with the advent of the threaded vulkan
hwaccel. As a plus, saves us some annoying #ifdef boilerplate.

I will raise the minimum vf_libplacebo version globally on the next
stable release of libplacebo, and remove all of these checks.

libavfilter/vf_libplacebo.c

@@ -544,23 +544,15 @@ fail:
     return err;
 }
 
-#if PL_API_VER >= 201
-# if PL_API_VER >= 278
+#if PL_API_VER >= 278
 static void lock_queue(void *priv, uint32_t qf, uint32_t qidx)
-# else
-static void lock_queue(void *priv, int qf, int qidx)
-# endif
 {
     AVHWDeviceContext *avhwctx = priv;
     const AVVulkanDeviceContext *hwctx = avhwctx->hwctx;
     hwctx->lock_queue(avhwctx, qf, qidx);
 }
 
-# if PL_API_VER >= 278
 static void unlock_queue(void *priv, uint32_t qf, uint32_t qidx)
-# else
-static void unlock_queue(void *priv, int qf, int qidx)
-# endif
 {
     AVHWDeviceContext *avhwctx = priv;
     const AVVulkanDeviceContext *hwctx = avhwctx->hwctx;
@@ -576,6 +568,7 @@ static int init_vulkan(AVFilterContext *avctx, const AVVulkanDeviceContext *hwct
     size_t buf_len;
 
     if (hwctx) {
+#if PL_API_VER >= 278
         /* Import libavfilter vulkan context into libplacebo */
         s->vulkan = pl_vulkan_import(s->log, pl_vulkan_import_params(
             .instance       = hwctx->inst,
@@ -585,11 +578,9 @@ static int init_vulkan(AVFilterContext *avctx, const AVVulkanDeviceContext *hwct
             .extensions     = hwctx->enabled_dev_extensions,
             .num_extensions = hwctx->nb_enabled_dev_extensions,
             .features       = &hwctx->device_features,
-#if PL_API_VER >= 201
             .lock_queue     = lock_queue,
             .unlock_queue   = unlock_queue,
             .queue_ctx      = avctx->hw_device_ctx->data,
-#endif
             .queue_graphics = {
                 .index = hwctx->queue_family_index,
                 .count = hwctx->nb_graphics_queues,
@@ -605,6 +596,13 @@ static int init_vulkan(AVFilterContext *avctx, const AVVulkanDeviceContext *hwct
             /* This is the highest version created by hwcontext_vulkan.c */
             .max_api_version = VK_API_VERSION_1_3,
         ));
+#else
+        av_log(s, AV_LOG_ERROR, "libplacebo version %s too old to import "
+               "Vulkan device, remove it or upgrade libplacebo to >= 5.278\n",
+               PL_VERSION);
+        err = AVERROR_EXTERNAL;
+        goto fail;
+#endif
     } else {
         s->vulkan = pl_vulkan_create(s->log, pl_vulkan_params(
             .queue_count = 0, /* enable all queues for parallelization */