hugetlbfs: cleanup some comments in inode.c

hugetlbfs: cleanup some comments in inode.c

The function generic_file_buffered_read has been renamed to filemap_read
since commit 87fa0f3eb267 ("mm/filemap: rename generic_file_buffered_read
to filemap_read").  Update the corresponding comment.  And duplicated
taken in hugetlbfs_fill_super is removed.

Link: https://lkml.kernel.org/r/20220726142918.51693-5-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>