hugetlbfs: Convert remove_inode_hugepages() to use filemap_get_folios()

Use folios throughout this function.  That removes the last caller of
huge_pagevec_release(), so delete that too.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian Brauner (Microsoft) <brauner@kernel.org>