block: default BLOCK_LEGACY_AUTOLOAD to y

As Luis reported, losetup currently doesn't properly create the loop
device without this if the device node already exists because old
scripts created it manually.  So default to y for now and remove the
aggressive removal schedule.

Reported-by: Luis Chamberlain <mcgrof@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Link: https://lore.kernel.org/r/20220225181440.1351591-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>