Remove platform checks when the backend is present. (triton-inference…

…-server#3118)

* Removed platform checks when the backend is present.

* Added explanation of why platform is not checked when backend is provided.

Co-authored-by: dyastremsky@nvidia.com <dyastremsky@dyastremsky-dt.dyn.nvidia.com>

src/core/model_config_utils.cc

@@ -998,7 +998,10 @@ ValidateModelConfig(
         "'max_batch_size' must be non-negative value for " + config.name());
   }
 
-  if (!config.platform().empty()) {
+  // If backend is empty, validate the platform. Otherwise, the platform
+  // validation should be performed by the backend, as Triton may not know
+  // about the backend's requirements.
+  if (!config.platform().empty() && config.backend().empty()) {
     if (!expected_platform.empty() &&
         (config.platform() != expected_platform)) {
       return Status(