UPSTREAM: squashfs: don't use intermediate buffer if pages missing

Now that the "page actor" can handle missing pages, we don't have to fall
back to using an intermediate buffer in Squashfs_readpage_block() if all
the pages necessary can't be obtained.

Link: https://lkml.kernel.org/r/20220611032133.5743-3-phillip@squashfs.org.uk


Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Cc: Hsin-Yi Wang <hsinyi@chromium.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Xiongwei Song <Xiongwei.Song@windriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Bug: 290900323
(cherry picked from commit 1bb1a07a)
Change-Id: Ie16c3e4adab0066680f070a6af2a7a21e99be50d
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>