aoe: Fix unitialized var usage

Commit 4f2ac93c175c4922bdddbfec6cad94b32cea0070 (block: Remove bi_idx
references) accidently removed the bit that set bv - readd that.

Signed-off-by: Kent Overstreet <koverstreet@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Ed L. Cashin" <ecashin@coraid.com>
Cc: fengguang.wu@intel.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/aoe/aoecmd.c

@@ -927,7 +927,7 @@ bufinit(struct buf *buf, struct request *rq, struct bio *bio)
 	buf->resid = bio->bi_size;
 	buf->sector = bio->bi_sector;
 	bio_pageinc(bio);
-	buf->bv = bio_iovec(bio);
+	buf->bv = bv = bio_iovec(bio);
 	buf->bv_resid = bv->bv_len;
 	WARN_ON(buf->bv_resid == 0);
 }