loop: Remove sector_t truncation checks

[ Upstream commit 083a6a50783ef54256eec3499e6575237e0e3d53 ]

sector_t is now always u64, so we don't need to check for truncation.

Signed-off-by: Martijn Coenen <maco@android.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Genjian Zhang <zhanggenjian@kylinos.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>