vl.c: error out if -mem-path is used together with -M memory-backend

the former is not actually used by explicit backend, so instead of
silently ignoring the option in non valid context, exit with error.

Signed-off-by: Igor Mammedov <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: Igor Mammedov

softmmu/vl.c

@@ -4315,6 +4315,11 @@ void qemu_init(int argc, char **argv, char **envp)
                              "explicitly specified 'memory-backend' property");
                 exit(EXIT_FAILURE);
         }
+        if (mem_path) {
+            error_report("'-mem-path' can't be used together with"
+                         "'-machine memory-backend'");
+            exit(EXIT_FAILURE);
+        }
         ram_size = backend_size;
     }