qemu: process: Fix the return value in qemuProcessSEVCreateFile

When commit 6718132d enforced usage of the cleanup label, it forgot to
set the @ret variable to 0 on "success" exit path.

Signed-off-by: Luyao Huang <lhuang@redhat.com>
Reviewed-by: Erik Skultety <eskultet@redhat.com>

src/qemu/qemu_process.c

@@ -5842,6 +5842,7 @@ qemuProcessSEVCreateFile(const char *configDir,
         goto cleanup;
     }
 
+    ret = 0;
  cleanup:
     VIR_FREE(configFile);
     return ret;