mm: fix VM_BUG_ON in __delete_from_swap_cache()

mm: fix VM_BUG_ON in __delete_from_swap_cache()

Patch series "Folio fixes for 6.0".

This patch (of 2):

The recent folio conversion changed the VM_BUG_ON() to dump the folio
we're storing instead of the entry we retrieved.  This was a mistake;
the entry we retrieved is the more interesting page to dump.

Link: https://lkml.kernel.org/r/20220902192639.1737108-1-willy@infradead.org
Link: https://lkml.kernel.org/r/20220902192639.1737108-2-willy@infradead.org
Fixes: ceff9d3354e9 ("mm/swap: convert __delete_from_swap_cache() to a folio")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>