btrfs: convert find_lock_delalloc_range() to use a folio

btrfs: convert find_lock_delalloc_range() to use a folio

Instead of passing in a page for locked_page, pass in the folio instead.
We only use the folio itself to validate some range assumptions, and
then pass it into other functions.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>