nvme-rdma: correctly check for target keyed sgl support

The code was checking bit 20 instead of bit 2.  Also fixed the log entry.

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>