block: cleanup __blkdev_issue_discard()

block: cleanup __blkdev_issue_discard()

Cleanup __blkdev_issue_discard() a bit:

- remove local variable of 'end_sect'
- remove code block of 'fail'

Cc: Mike Snitzer <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Xiao Ni <[email protected]>
Cc: Mariusz Dabrowski <[email protected]>
Tested-by: Rui Salvaterra <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>