block: cleanup REQ_SOFTBARRIER usages

blk_insert_request() doesn't need to worry about REQ_SOFTBARRIER.
Don't set it.  Combined with recent ide updates, REQ_SOFTBARRIER is
now only used in elevator proper and for discard requests.

[ Impact: cleanup ]

Signed-off-by: Tejun Heo <tj@kernel.org>
1 file changed