block: Fix elevator_get_default() checking for NULL q->tag_set

elevator_get_default() and elv_support_iosched() both check for whether
or not q->tag_set is non-NULL, however it's not possible for them to be
NULL. This messes up some static checkers, as the checking of tag_set
isn't consistent.

Remove the checks, which both simplifies the logic and avoids checker
errors.

Signed-off-by: SurajSonawane2415 <surajsonawane0215@gmail.com>
Link: https://lore.kernel.org/r/20241007111416.13814-1-surajsonawane0215@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>