ms_block: remove unused pointer 'set'

Pointer 'set' is declared but not used, remove it. Cleans up warning:

warning: unused variable ‘set’ [-Wunused-variable]
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

drivers/memstick/core/ms_block.c

@@ -2104,7 +2104,6 @@ static const struct blk_mq_ops msb_mq_ops = {
 static int msb_init_disk(struct memstick_dev *card)
 {
 	struct msb_data *msb = memstick_get_drvdata(card);
-	struct blk_mq_tag_set *set = NULL;
 	int rc;
 	unsigned long capacity;