vulkan: Add a comment explainint SEVERITY_WARNING_BIT for vk_error*()

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31449>

src/vulkan/runtime/vk_log.c

@@ -309,6 +309,25 @@ __vk_errorv(const void *_obj, VkResult error,
 
    const char *error_str = vk_Result_to_str(error);
 
+   /* From the Vulkan 1.3.295 spec:
+    *
+    *    "VK_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT specifies use of
+    *    Vulkan that may expose an application bug. Such cases may not be
+    *    immediately harmful, such as a fragment shader outputting to a
+    *    location with no attachment. Other cases may point to behavior that
+    *    is almost certainly bad when unintended such as using an image whose
+    *    memory has not been filled. In general if you see a warning but you
+    *    know that the behavior is intended/desired, then simply ignore the
+    *    warning.
+    *
+    *    VK_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT specifies that the
+    *    application has violated a valid usage condition of the
+    *    specification."
+    *
+    * Our use of vk_error*() to expound on error messages returned from
+    * drivers falls more under the WARNING category than ERROR since they may
+    * not actually be application bugs or VU violations.
+    */
    if (format) {
       char *message = ralloc_vasprintf(NULL, format, va);