mm/memfd: clarify error handling labels in memfd_create()

err_name --> err_free_name (fd failure case)
err_fd --> err_free_fd (file failure case)

Link: https://lkml.kernel.org/r/20250610083730.527619-1-ye.liu@linux.dev


Signed-off-by: Ye Liu <liuye@kylinos.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>