fs: aio: use a folio in aio_free_ring()

Use a folio throughout aio_free_ring() to remove calls to compound_head(),
also move pr_debug after folio check to remove unnecessary print.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Link: https://lore.kernel.org/r/20240321131640.948634-3-wangkefeng.wang@huawei.com


Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>