block: remove unnecessary NULL checks in bioset_integrity_free()

mempool_destroy() already checks for a NULL value being passed in, this
eliminates duplicate checks.

This was caught by running make coccicheck M=block/ on linus' tree on
commit 77ede3a014a32746002f7889211f0cecf4803163 (current head as of this
patch).

Reviewed-by: Kyle Fortin <kyle.fortin@oracle.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Tim Hansen <devtimhansen@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/bio-integrity.c

@@ -485,11 +485,8 @@ EXPORT_SYMBOL(bioset_integrity_create);
 
 void bioset_integrity_free(struct bio_set *bs)
 {
-	if (bs->bio_integrity_pool)
-		mempool_destroy(bs->bio_integrity_pool);
-
-	if (bs->bvec_integrity_pool)
-		mempool_destroy(bs->bvec_integrity_pool);
+	mempool_destroy(bs->bio_integrity_pool);
+	mempool_destroy(bs->bvec_integrity_pool);
 }
 EXPORT_SYMBOL(bioset_integrity_free);