Merge patch series "Squashfs: Update code to not use page->index"

Phillip Lougher <phillip@squashfs.org.uk> says:

In the near future page->index will be removed [1].  Any code which
still uses page->index needs to be updated.

This patch-set contains 4 patches which updates most of the code in
Squashfs.  The exceptions are functions which have been fixed in
recent patches [2] & [3].

[1]: https://lore.kernel.org/all/Zp8fgUSIBGQ1TN0D@casper.infradead.org/
[2]: https://lore.kernel.org/all/20240817101146.2347378-1-lizetao1@huawei.com/
[3]: https://lore.kernel.org/all/20240817101146.2347378-2-lizetao1@huawei.com/

* patchesf from https://lore.kernel.org/r/20240818235847.170468-1-phillip@squashfs.org.uk:
  Squashfs: Rewrite and update squashfs_readahead_fragment() to not use page->index
  Squashfs: Update squashfs_readpage_block() to not use page->index
  Squashfs: Update squashfs_readahead() to not use page->index
  Squashfs: Update page_actor to not use page->index

Link: https://lore.kernel.org/r/20240818235847.170468-1-phillip@squashfs.org.uk
Signed-off-by: Christian Brauner <brauner@kernel.org>