block: get rid of redundant else

This is a pure code cleanup patch and doesn't change any functionality.
This removes the redundant else in the code which is not needed since
we are returning from function anyway.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>